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34877 Publications

Influence of structure and cation distribution on magnetic anisotropy and damping in Zn/Al doped nickel ferrites

Lumetzberger, J.; Buchner, M.; Pile, S.; Ney, V.; Gaderbauer, W.; Daffé, N.; Moro, M. V.; Primetzhofer, D.; Lenz, K.; Ney, A.

An in-depth analysis of Zn/Al doped nickel ferrite thin films grown by reactive magnetron sputtering was conducted to gain insight into the magnetic properties interesting for applications in spintronics. The material is insulating, ferromagnetic at room temperature and has a low magnetic damping with additional strong magnetoelastic coupling. The sample system is analyzed with regard to crystal structure, chemical composition and static as well as dynamic magnetic properties. Thus a correlation between composition, strain, cation distribution, magnetocrystalline anisotropy and damping is evidenced. X-ray magnetic circular dichroism spectra and field dependent curves at the L3;2 edges of Ni and Fe are performed to complement integral magnetometry measurements and identify their magnetic contributions to the hysteresis. In particular, a strong in uence of the lattice site occupation of Ni2+ Td and cation coordination of Fe2+ Oh on the intrinsic damping is found. Furthermore, the vital role of the incorporation of Zn2+ and Al3+ is evidenced by comparison with a sample of altered composition. A strain-independent reduction of the magnetic anisotropy and damping by adapting the cation distribution is demonstrated.

Keywords: ferrites; ferromagnetic resonance; x-rays; XMCD; cation distribution; damping; hysteresis; magnetic properties; thin films

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Permalink: https://www.hzdr.de/publications/Publ-30870
Publ.-Id: 30870


Formation of PuSiO4 under hydrothermal conditions

Estevenon, P.; Welcomme, E.; Tamain, C.; Jouan, G.; Szenknect, S.; Mesbah, A.; Poinssot, C.; Moisy, P.; Dacheux, N.

Attempts to synthesize plutonium (IV) silicate, PuSiO4, have been performed on the basis of the results recently reported in the literature for CeSiO4, ThSiO4 and USiO4 under hydrothermal conditions. Although it was not possible to prepare PuSiO4 by applying the conditions reported for thorium and uranium, an efficient way of PuSiO4 synthesis was established following those optimized for CeSiO4 system. This method was based on the slow oxidation of plutonium (III) silicate reactants under hydrothermal conditions at 150°C in hydrochloric acid (pH = 3 – 4). This result shed a new light on the potential behavior of plutonium in reductive environment, highlighted the representativeness of cerium surrogates to study plutonium in such conditions and brought some important pieces of information on plutonium chemistry in silicate solutions.

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Permalink: https://www.hzdr.de/publications/Publ-30869
Publ.-Id: 30869


High-sensitivity investigation of low-lying dipole strengths in 120Sn

Müscher, M.; Wilhelmy, J.; Savran, D.; Schwengner, R.; Massarczyk, R.; Grieger, M.; Isaak, J.; Junghans, A. R.; Kögler, T.; Ludwig, F.; Symochko, D.; Takacs, M. P.; Tamkas, M.; Wagner, A.; Zilges, A.

Background: The term Pygmy Dipole Resonance (PDR) denotes electric dipole excitations below and around the neutron separation threshold. It may be important, e.g., for the nucleosynthesis of heavy nuclei or the symmetry energy in the Equation of State (EoS). For a deeper understanding of the PDR systematic studies are essential.
Purpose: The tin isotopic chain is a well-suited candidate to investigate the systematics of the PDR and the (g,g') reactions on 112,116,120,124Sn have already been measured in experiments using bremsstrahlung. It was claimed that the extracted electric dipole transition strengths of these isotopes increase with increasing neutron-to-proton ratio with the exception of 120 Sn. Furthermore, previous results from elastic photon scattering experiments on 120Sn are in disagreement with corresponding (p,p') Coulomb excitation data. To examine this discrepancy an additional high-sensitivity bremsstrahlung experiment on 120Sn was performed.
Method: The Nuclear Resonance Fluorescence (NRF) method is used which bases on real photon scattering. The bremsstrahlung experiment presented in this work was performed with a maximum energy of E = 9.5 MeV at the gELBE facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Besides a state-to-state analysis, the quasi-continuum was investigated as well.
Results: Above Ex = 4 MeV 236 dipole transitions were clearly identified and 168 of those were observed for the first time. Assuming that all analyzed transitions have electric dipole character the summed electric dipole strength equals B(E1) = 374(35) e2 fm2 (0.54(5) % of the TRK sum rule) for transitions from 4 MeV to Sn = 9.1 MeV. This is an enhancement of a factor 2.3 compared to the previously published 120Sn(g,g') results.
Especially, the observation of many weaker transitions in the state-to-state analysis lead to this increase. The photo-absorption cross sections deduced from the quasi-continuum analysis are about two times higher than the results of the (p,p') experiment.
Conclusion: The newly extracted summed B(E1) value of the state-to-state analysis is larger than those of 112,116Sn and smaller than that of 124 Sn. The difference between the present (g,g') data and the results of the inelastic proton scattering experiment above 6.3 MeV is still striking. The deviation may be explained by unobserved decay branchings and unresolved strength. Up to now, there is no explanation for the discrepancy between the extracted photo-absorption cross sections of the analysis of the quasi-continuum and the (p,p')
measurement. Additional experiments may shed light on this deviation.

Keywords: Photon scattering; Photoabsorption cross section; Electromagnetic transition strengths

Permalink: https://www.hzdr.de/publications/Publ-30867
Publ.-Id: 30867


Unveiling reductant chemistry in fabricating noble metal aerogels for superior oxygen evolution and ethanol oxidation

Du, R.; Wang, J.; Wang, Y.; Hübner, R.; Fan, X.; Senkovska, I.; Hu, Y.; Kaskel, S.; Eychmüller, A.

Amongst various porous materials, noble metal aerogels attract wide attention due to their concurrently featured catalytic properties and large surface areas. However, insufficient understanding and investigation of key factors (e.g. reductants and ligands) in the fabrication process limits on-target design, impeding material diversity and available applications. Herein, unveiling multiple roles of reductants, we develop an efficient method, i.e. the excessive-reductant-directed gelation strategy. It enables to integrate ligand chemistry for creating gold aerogels with a record-high specific surface area (59.8 m2 g−1), and to expand the composition to all common noble metals. Moreover, we demonstrate impressive electrocatalytic performance of these aerogels for the ethanol oxidation and oxygen evolution reaction, and discover an unconventional organic-ligand-enhancing effect. The present work not only enriches the composition and structural diversity of noble metal aerogels, but also opens up new dimensions for devising efficient electrocatalysts for broad material systems.

Permalink: https://www.hzdr.de/publications/Publ-30866
Publ.-Id: 30866


Development of a radiofluorinated adenosine A2B receptor antagonist as potential ligand for PET imaging

Lindemann, M.; Moldovan, R.-P.; Hinz, S.; Deuther-Conrad, W.; Gündel, D.; Dukic-Stefanovic, S.; Toussaint, M.; Teodoro, R.; Juhl, C.; Steinbach, J.; Brust, P.; Müller, C. E.; Wenzel, B.

The adenosine A2B receptor has been proposed as a novel therapeutic target in cancer, as for example, its expression is drastically elevated in several tumors and cancer cells. Noninvasive molecular imaging by using positron emission tomography (PET) would allow the in vivo quantification of this receptor in pathological processes and most likely enable the identification and clinical monitoring of respective cancer therapies. On the basis of a bicyclic pyridopyrimidine-2,4-dione core structure, the new adenosine A2B receptor ligand 9 was synthesized containing a 2-fluoropyridine moiety suitable for labeling with the short-lived PET radionuclide fluorine-18. Compound 9 showed a high binding affinity for the human A2B receptor (Ki(A2B) = 2.51 nM) along with high selectivities versus the A1, A2A, and A3 receptor subtypes. Therefore, it was radiofluorinated via nucleophilic aromatic substitution of the corresponding nitro precursor using [18F]F-/K2.2.2./K2CO3 in DMSO at 120 °C. Metabolism studies of [18F]9 in mice revealed about 60 % of intact radiotracer in plasma at 30 minutes p.i. A preliminary PET study in healthy mice showed an overall biodistribution of [18F]9 corresponding to the known ubiquitous but low expression of the A2B receptor. Consequently, [18F]9 represents a novel PET radiotracer with high affinity and selectivity toward the adenosine A2B receptor and a suitable in vivo profile. Subsequent studies are envisaged to investigate the applicability of [18F]9 to detect alterations in the receptor density in certain cancer-related disease models.

Keywords: A2B receptor; adenosine; PET; fluorine-18; metabolism; radiofluorination

Permalink: https://www.hzdr.de/publications/Publ-30865
Publ.-Id: 30865


Microstructure and Nanoscopic Porosity in Black Pd Films

Melikhova, O.; Čížek, J.; Hruška, P.; Lukáč, F.; Novotný, M.; More-Chevalier, J.; Fitl, P.; Liedke, M. O.; Butterling, M.; Wagner, A.

In the present work the microstructure of a black Pd film prepared by thermal evaporation and a glossy Pd film deposited by magnetron sputtering was compared. While the glossy Pd film exhibits typical polycrystalline structure with column-like grains, the black Pd film has fractal-like porous structure. Positron annihilation spectroscopy revealed that positronium is formed in nanoscopic cavities of the black Pd film. In conventional metals positronium does not form due to screening by conduction electrons. However, in porous metals containing nanoscopic porosity a thermalized positron may pick an electron on inner surface of a pore and escape into a cavity forming positronium. The average size of nanoscopic pores in the black Pd film was determined from the lifetime of long-lived ortho-positronium component.

Keywords: thin film; positron annihilation; porosity; black metal; black gold; magnetron sputtering

Permalink: https://www.hzdr.de/publications/Publ-30864
Publ.-Id: 30864


Defects in Thin Layers of High Entropy Alloy HfNbTaTiZr

Lukáč, F.; Hruška, P.; Cichoň, S.; Vlasák, T.; Cížek, J.; Kmječ, T.; Melikhova, O.; Butterling, M.; Liedke, M. O.; Wagner, A.

High entropy alloys represent a new type of materials with unique combination of physical properties originating due to occurrence of single phase solid solution of numerous elements. Preparation of high entropy alloys films with nanosized grains promises increased effective surface and high intergranular diffusion of elements. In the present work HfNbTaTiZr films were deposited by magnetron sputtering from single phase HfNbTaTiZr target prepared by spark plasma sintering. Chemical composition of high entropy alloys thin films prepared this way was enriched in Ti and depleted in Zr and Nb. Very fine microstructure of the film was documented and defect distribution was found to be non-uniform with depth.

Keywords: high entropy alloy; thin film; positron annihilation; nano grain

Permalink: https://www.hzdr.de/publications/Publ-30863
Publ.-Id: 30863


Positron Structural Analysis of ScN Films Deposited on MgO Substrate

More-Chevalier, J.; Horák, L.; Cichoň, S.; Hruška, P.; Čížek, J.; Liedke, M. O.; Butterling, M.; Wagner, A.; Bulíř, J.; Hubík, P.; Gedeonová, Z.; Lančok, J.

Scandium nitride (ScN) is a semiconductor with a rocksalt-structure that has attracted attention for its potential applications in thermoelectric energy conversion devices, as a semiconducting component in epitaxial metal/semiconductor superlattices. Two ScN films of 118 nm and 950 nm thicknesses were deposited at the same conditions on MgO (001) substrate by reactive magnetron sputtering. Poly-orientation of films was observed with first an epitaxial growth on MgO and then a change in the orientation growth due to the decrease of the adatom mobility during the film growth. Positron lifetime measurements showed a high concentration of nitrogen vacancies in both films with a slightly higher concentration for the thicker ScN film. Presence of nitrogen vacancies explains the values of direct band gaps of 2:53+-0:01 eV, and 2:56+-0:01 eV which has been measured on ScN films of 118 nm and 950 nm thicknesses, respectively.

Keywords: positron annihilation; semiconductor; ScN; band gap; defects; vacancies

Permalink: https://www.hzdr.de/publications/Publ-30862
Publ.-Id: 30862


Cation exchange protocols to radiolabel aqueous stabilized ZnS, ZnSe and CuFeS2 nanocrystals with 64Cu for dual radio- and photo-thermal therapy

Avellini, T.; Soni, N.; Silvestri, N.; Fiorito, S.; de Donato, F.; de Mei, C.; Cassani, M.; Ghosh, S.; Walther, M.; Manna, L.; Stephan, H.; Pellegrino, T.

In metal chalcogenide nanocrystals (NCs), the cations can be partially or fully replaced with other cations through the so-called cation exchange (CE) reactions. Here, we took advantage of these CE reactions to replace the cations on different chalcogenides NCs with 64Cu ions in order to radiolabel them. With respect to other approaches reported in the literature, our CE protocol is easily transferable to the clinic. It requires indeed one single step, in which the water-soluble NCs are mixed with a 64Cu copper(II) chloride solution of high specific activity, in the presence of vitamin C used as a reducing agent for Cu(II) to Cu(I)). Given the quantitative replacement of the cations of the NCs with 64Cu(I), a high radiochemical yield up to 90-95% can be reached. Provided that there is no free 64Cu, no purification step is needed, making the protocol straightforward. At the same time, the amount of NCs required for the exchange is so low (in the range of μg) that the dose of NCs shows no intrinsic cytotoxicity. This protocol works on different types of metal chalcogenide NCs. In ZnSe and ZnS NCs, the Zn(II) ions are exchanged with 64Cu (I) ions, and in CuFeS2 NCs the Fe(III) ions are exchanged with 64Cu(I). To ensure the stability of the NCs during and after the CE reaction, a multi-anchoring coating procedure based on PEG, cysteamine and poly-maleic anhydride was proven to be more efficient than the use of monothiol PEG ligands. With our approach we managed to achieve an unprecedented high specific activity, i.e. the amount of 64Cu radionuclide loaded per NC dose, to dispatch remarkable ionizing effects. Indeed, by exploiting a volumetric cations exchange, our strategy enables to concentrate a large dose of 64Cu (18.5 MBq) in a small NC dose (0.4 μg), reaching a specific activity of about 50 TBq/g. Remarkably, for CuFeS2 NCs even after the CE, the radiolabeled 64Cu:CuFeS2 NCs still show the characteristic dielectric resonance that enables the generation of heat under laser exposure for clinical use (1 W/cm2). The synergic toxicity of photo-ablation and 64Cu radiation exposure is here demonstrated in an in vitro study on glioblastoma and epidermoid carcinoma tumor cells.

Permalink: https://www.hzdr.de/publications/Publ-30861
Publ.-Id: 30861


Interplay between MycN and c-Myc regulates radioresistance and cancer stem cell phenotype in neuroblastoma upon glutamine deprivation

Le, G. M.; Mukha, A.; Püschel, J.; Valli, E.; Kamili, A.; Vittorio, O.; Dubrovska, A.; Kavallaris, M.

Targeting glutamine metabolism has emerged as a potential therapeutic strategy for Myc overexpressing cancer cells. Myc proteins contribute to an aggressive neuroblastoma phenotype. Radiotherapy is one of the treatment modalities for high-risk neuroblastoma patients. Herein, we investigated the effect of glutamine deprivation in combination with irradiation in neuroblastoma cells representative of high-risk disease and studied the role of Myc member interplay in regulating neuroblastoma cell radioresistance. Methods: Cell proliferation and viability assays were used to establish the effect of glutamine deprivation in neuroblastoma cells expressing c-Myc or MycN. Gene silencing and overexpression were used to modulate the expression of Myc genes to determine their role in neuroblastoma radioresistance. qPCR and western blot investigated interplay between expression of Myc members. The impact of glutamine deprivation on cell response following irradiation was explored using a radiobiological 3D colony assay. DNA repair gene pathways as well as CSC-related genes were studied by qPCR array. Reactive Oxygen Species (ROS) and glutathione (GSH) levels were detected by fluorescence and luminescence probes respectively. Cancer-stem cell (CSC) properties were investigated by sphere-forming assay and flow cytometry to quantify CSC markers. Expression of DNA repair genes and CSC-related genes was analysed by mining publicly available patient datasets. Results: Our results showed that glutamine deprivation decreased neuroblastoma cell proliferation and viability and modulated Myc member expression. We then demonstrated for the first time that combined glutamine deprivation with irradiation led to a selective radioresistance of MYCN-amplified neuroblastoma cells. By exploring the underlying mechanism of neuroblastoma radioresistance properties, our results highlight interplay between c-Myc and MycN expression suggesting compensatory mechanisms in Myc proteins leading to radioresistance in MYCN-amplified cells. This result was associated with the ability of MYCN-amplified cells to dysregulate the DNA repair gene pathway, maintain GSH and ROS levels and to increase the CSC-like population and properties. Conversely, glutamine deprivation led to radiosensitization in non-MYCN amplified cell lines through a disruption of the cell redox balance and a trend to decrease in the CSC-like populations. Mining publicly available gene expression dataset obtained from pediatric neuroblastoma patients, we identified a correlation pattern between Myc members and CSC-related genes as well as a specific group of DNA repair gene pathways. Conclusions: This study demonstrated that MycN and c-Myc tightly cooperate in regulation of the neuroblastoma CSC phenotypes and radioresistance upon glutamine deprivation. Pharmacologically, strategies targeting glutamine metabolism may prove beneficial in Myc-driven tumors. Consideration of MycN/c-Myc status in selecting neuroblastoma patients for glutamine metabolism treatment will be important to avoid potential radioresistance.

Keywords: Myc members; glutamine metabolism; neuroblastoma; radioresistance; Cancer-Stem Cells

Permalink: https://www.hzdr.de/publications/Publ-30860
Publ.-Id: 30860


Enhanced room temperature ferromagnetism in MoS2 by N plasma treatment

Wang, B.; Zhang, D.; Wang, H.; Zhao, H.; Liu, R.; Li, Q.; Zhou, S.; Du, J.; Xu, Q.

The introduction of ferromagnetism in MoS2 is important for its applications in semiconductor spintronics. MoS2 powders were synthesized by hydrothermal method, followed by the N plasma treatment at room temperature. Weak ferromagnetism with saturated ferromagnetic magnetization of 0.64 memu/g has been observed in the as-synthesized MoS2 at room temperature, which is significant enhanced to 3.67 memu/g after the N plasma treatment for the proper duration. X-ray photoelectron spectroscopy demonstrates the adsorption of N, and higher valence state of Mo than +4 due to the bonding with N after the N plasma treatment. First principle calculation has been performed to disclose the possible origin of ferromagnetism. One chemical adsorbed N ion on S ion may form conjugated π bonds with adjacent two Mo ions to have a total magnetic moment of 0.75 μB, contributing to the enhanced ferromagnetism.

Permalink: https://www.hzdr.de/publications/Publ-30859
Publ.-Id: 30859


3D-Ising critical behavior in antiperovskite-type ferromagneticlike Mn3GaN

Yuan, Y.; Liu, Y.; Xu, C.; Kang, J.; Wang, W.; Wang, Q.; Song, B.; Zhou, S.; Wang, X.

In this work, a systematic investigation on magnetic critical behavior is performed for the first time on an antiperovskite-type Mn3GaN, which is prepared by intentionally modifying stoichiometry. According to the XRD results, the antiperovskite structure is well preserved, even though all lattice parameters shrink upon reducing Ga and N content down to 60%. The sample exhibits a ferromagneticlike feature with a Curie temperature (T_C) of 394 K rather than frustrated behavior in stoichiometric Mn3GaN. Most importantly, the modified Arrott plots, Kouvel–Fisher plots, as well as critical isotherm method self-consistently co-confirm the critical exponents of β = 0.33, γ = 1.23, and δ = 4.7, unambiguously indicating that the critical behavior follows the 3D-Ising model around T_C.

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Permalink: https://www.hzdr.de/publications/Publ-30858
Publ.-Id: 30858


An Infrared Transmission Study of Ge:Mn Thick Films Prepared by Ion Implantation and Post-Annealing

Obied, L. H.; Roorda, S.; Prucnal, S.; Zhou, S.; Crandles, D. A.

Ge:Mn thick films (t$\approx 3\mu$m) with low average Mn concentration (< 0.3 %) were prepared by ion implantation at 77K followed by either conventional or flash lamp annealing. The films were characterized by Xray diffraction, Secondary Ion Mass Spectrometry, magnetometry and infrared transmission (100-6500 cm^{-1}). Post-annealing at high enough temperature recrystallizes the amorphous Ge:Mn films without significant migration of Mn to the surface while solid phase epitaxy does not occur, resulting in polycrystalline films. Annealing causes an estimated 50-80\% of the implanted Mn to migrate to Mn-rich clusters or form Mn_5Ge_3 while the remainder enters the Ge lattice substitutionally creating free holes. Evidence for free holes comes from structure in the mid-infrared absorption coefficient that is similar to previous observations in p-type Ge. The data suggest that the maximum solubility of Mn in the Ge crystalline lattice has an upper limit of <0.08%.

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Permalink: https://www.hzdr.de/publications/Publ-30857
Publ.-Id: 30857


Size Dependence of Lattice Parameter and Electronic Structure in CeO2 Nanoparticles

Prieur, D.; Bonani, W.; Popa, K.; Walter, O.; Kriegsman, K.; Engelhard, M.; Guo, X.; Eloirdi, R.; Gouder, T.; Beck, A.; Vitova, T.; Scheinost, A.; Kvashnina, K.; Martin, P.

Intrinsic properties of a compound (e.g. electronic structure, crystallographic structure, optical and magnetic properties) define notably its chemical and physical behavior. In the case of nanomaterials, these fundamental properties depend on the occurrence of quantum mechanical size effects and on the considerable increase of the surface to bulk ratio.
Here, we explore the size-dependence of both crystal and electronic properties of CeO2 nanoparticles (NPs) with different sizes by state-of-the art spectroscopic techniques. XRD, XPS and HERFD-XANES demonstrate that the as-synthesized NPs crystallize in the fluorite structure and they are predominantly composed of CeIV ions. The strong dependence of the lattice parameter with the NPs size was attributed to the presence of adsorbed species at the NPs surface thanks to FTIR and TGA measurements. In addition, the size-dependence of the t2g states in the Ce LIII XANES spectra was experimentally observed by HERFD-XANES and confirmed by theoretical calculations.

Keywords: Lanthanide; CeO2; HEFRD-XANES; Electronic Structure

Permalink: https://www.hzdr.de/publications/Publ-30856
Publ.-Id: 30856


Quadrupolar response from the crystal electric field level scheme consisting of only Kramers doublets in DyNiAl

Suzuki, D.; Ishii, I.; Kumano, S.; Umeno, T.; Andreev, A. V.; Gorbunov, D.; Suzuki, T.

The rare earth compound DyNiAl shows ferromagnetic and antiferromagnetic phase transitions at TC = 30 K and T1 = 15 K, respectively. Elastic properties of DyNiAl have been investigated by means of ultrasonic spectroscopy. The transverse elastic modulus C44 shows an elastic softening below 60 K and exhibits a bend at TC. The softening continues down to T1 and an elastic hardening is observed below T1. The softening above TC is well reproduced by Curie-Weiss-type equation including a quadrupole interaction. A quadrupole-quadrupole coupling constant obtained from C44 is negative, suggesting an antiferroquadrupolar-type interaction between quadrupoles Oyz or Ozx.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011165
    DOI: 10.7566/JPSCP.30.011165

Permalink: https://www.hzdr.de/publications/Publ-30855
Publ.-Id: 30855


Magnetocaloric Effect in Alloy Fe49Rh51in Pulsed Magnetic Fields up to 50 T

Kamantsev, A. P.; Amirov, A. A.; Koshkid'Ko, Y. S.; Salazar Mejia, C.; Mashirov, A. V.; Aliev, A. M.; Koledov, V. V.; Shavrov, V. G.

Magnetocaloric effect (MCE) in pulsed magnetic fields up to 50 T was directly studied in alloyFe49Rh51. An inverse MCE ΔT ≈ –8 K is observed at different initial temperatures around the metamagneticphase transition upon field rising to 20 T; further growth of the field to 50 T leads to a decrease in the absoluteadiabatic temperature change by nearly 1 K, which is due to the direct MCE and proves that the whole sampleundergoes a transition into the ferromagnetic phase. Upon the field decrease, the maximal absolute value ofthe adiabatic temperature change of |ΔT| = 9.8 K was revealed at 6 T when the initial temperature is 310 K.

Permalink: https://www.hzdr.de/publications/Publ-30854
Publ.-Id: 30854


Development of novel analogs of the monocarboxylate transporter ligand FACH and biological validation of one potential radiotracer for PET imaging

Sadeghzadeh, M.; Wenzel, B.; Gündel, D.; Deuther-Conrad, W.; Toussaint, M.; Moldovan, R.-P.; Fischer, S.; Teodoro, R.; Jonnalagadda, S.; Jonnalagadda, S. K.; Mereddy, V. R.; Drewes, L. R.; Brust, P.

Monocarboxylate transporters 1-4 (MCT1-4) are involved in several metabolism-related diseases, especially cancer, providing the chance to be considered as relevant targets for diagnosis and therapy. [18F]FACH was recently developed and showed very promising preclinical results as a potential PET radiotracer for imaging of MCTs, which encouraged us to develop the novel analogs 1 and 2 of FACH. They were synthesized via Buchwald-Hartwig amination starting from m-anisidine followed by Vilsmeier-Haack formylation and Knoevenagel condensation in moderate overall yields. MCT1 inhibition was estimated by [14C]lactate uptake assay on rat brain endothelial (RBE4) cells. Although 2 showed 25-times lower MCT1 inhibitory potency than FACH (IC50 = 11 nM), compound 1 could be a suitable PET candidate with an IC50 value of 118 nM. Therefore, 1 was selected for radiosynthesis of [18F]1 and subsequent biological evaluation as a potential PET radiotracer for imaging of the MCT expression in mouse brain. By in vitro autoradiography in cryosections of the mouse kidney, 50% displacement of [18F]1 by 10 µM of the specific MCT1 inhibitor α-cyano-4-hydroxycinnamic acid (α-CHC) was observed. Despite a higher lipophilicity of [18F]1 compared to [18F]FACH, in vivo brain uptake of [18F]1 was in a similar range, likely to be related to similar transport rates by MCTs on RBE4 cells. The high uptake of the new radiotracer in kidney and other peripheral MCT-expressing organs together with significant reduction by α-CHC, suggests the suitability of [18F]1 for imaging of the MCTs expression in vivo.

Keywords: monocarboxylate transporters (MCTs); FACH; 18F-labeled analog of FACH; α-CHC; blood-brain barrier (BBB); positron emission tomography (PET) imaging

Permalink: https://www.hzdr.de/publications/Publ-30853
Publ.-Id: 30853


Local Structure in U(IV) and U(V) Environments: The Case of U3O7

Leinders, G.; Bes, R.; Kvashnina, K.; Verwerft, M.

A comprehensive analysis of X-ray absorption data obtained at theUL3-edge for a systematic series of single-valence (UO2, KUO3,UO3) and mixed-valence uranium compounds (U4O9,U3O7,U3O8) is reported. High-energyresolutionfluorescence detection (HERFD) X-ray absorption near-edge spectros-copy (XANES) and extended X-ray absorptionfine structure (EXAFS) methodswere applied to evaluate U(IV) and U(V) environments, and in particular, toinvestigate the U3O7local structure. Wefind that the valence state distribution inmixed-valence uranium compounds cannot be confidently quantified from aprincipal component analysis of the UL3-edge XANES data. The spectral linebroadening, even when applying the HERFD-XANES method, is sensibly higher(∼3.9 eV) than the observed chemical shifts (∼2.4 eV). Additionally, the white line shape and position are affected not only by thechemical state, but also by crystalfield effects, which appear well-resolved in KUO3. The EXAFS of a phase-pure U3O7sample wasassessed based on an average representation of the expanded U60O140structure. Interatomic U−O distances are found mainly tooccur at 2.18 (2), 2.33 (1), and 3.33 (5) Å, and can be seen to correspond to the spatial arrangement of cuboctahedral oxygenclusters. The interatomic distances derived from the EXAFS investigation support a mixed U(IV)−U(V) valence character in U3O7

Permalink: https://www.hzdr.de/publications/Publ-30852
Publ.-Id: 30852


Topological Hall effect in single thick SrRuO3 layers induced by defect engineering

Wang, C.; Chang, C.-H.; Herklotz, A.; Chen, C.; Ganss, F.; Kentsch, U.; Chen, D.; Gao, X.; Zeng, Y.-J.; Hellwig, O.; Helm, M.; Gemming, S.; Chu, Y.-H.; Zhou, S.

The topological Hall effect (THE) has been discovered in ultrathin SrRuO3 (SRO) films, where the interface between the SRO layer and another oxide layer breaks the inversion symmetry resulting in the appearance of THE. Thus, THE only occurs in ultra-thin SRO films of several unit cells. In addition to employing a heterostructure, the inversion symmetry can be broken intrinsically in bulk by introducing defects. In this study THE is observed in 60 nm thick SRO films, in which defects and lattice distortions are introduced by helium ion irradiation. The irradiated SRO films exhibit a pronounced THE in a wide temperature range from 5 K to 80 K. These observations can be attributed to the emergence of Dzyaloshinskii-Moriya interaction as a result of artificial inversion symmetry breaking associated with the lattice defect engineering. The creation and control of the THE in oxide single layers can be realized by ex situ film processing. Therefore, this work provides new insights into the THE and illustrates a promising strategy to design novel spintronic devices.

Keywords: defect engineering; Dzyaloshinskii-Moriya interaction; lattice distortion; oxide thin film; topological Hall effect

Permalink: https://www.hzdr.de/publications/Publ-30851
Publ.-Id: 30851


CFD simulation of aeration and mixing processes in a full-scale oxidation ditch

Höhne, T.; Mamedov, T.

This study aims to build a computational fluid dynamics (CFD) model that can be used to predict fluid flow pattern and to analyse the mixing process in a full-scale OD. CFD is a widely used numerical tool for analysing, modelling and simulating fluid flow patterns in wastewater treatment processes. In this study, a three-dimensional (3D) computational geometry was used, and the Eulerian-Eulerian multiphase flow model was built. Pure water was considered as the continuous phase, whereas air was modelled as the dispersed phase. The Shear Stress Transport (SST) turbulence model was specified which predicts turbulence eddies in free stream and wall-bounded region with high accuracy. The momentum source term approach and the transient rotor-stator approach were implemented for the modelling of the submersible agitators. The hydrodynamic analysis was successfully performed for four different scenarios. In order to prevent the incorrect positioning of the submerged agitators, thrust analysis was also done. The results show that the minimum required water velocity was reached to maintain the solid particles suspended in the liquid media and adequate mixing was determined.

Keywords: CFD; Multiphase flow; Hydrodynamics; Oxidation ditch

Permalink: https://www.hzdr.de/publications/Publ-30850
Publ.-Id: 30850


The Crystal Electric Field Effect in the Distorted Kagome Lattice Ferromagnet Nd3Ru4Al12

Ishii, I.; Mizuno, T.; Kumano, S.; Umeno, T.; Suzuki, D.; Andreev, A. V.; Gorbunov, D.; Henriques, M. S.; Suzuki, T.

The distorted kagome lattice compound Nd3Ru4Al12 shows a ferromagnetic phase transition at TC =39 K. Reduced Nd magnetic moments with two different values of 2.66 and 0.95 µB are aligned along the c-axis below TC. It was previously reported that a crystal electric field (CEF) effect may affect the reduced magnetic moments. To clarify the 4f -electronic state in Nd3Ru4Al12, we performed CEF analyses for the inverse magnetic susceptibility and magnetization. We proposed the CEF level scheme of which the inverse magnetic susceptibilities along both a- and c-axes are reproduced. The ferromagnetic phase transition at TC along the c-axis can be explained by a simple CEF model. In contrast, reduced magnetic moments cannot be understood by the simple CEF model, because calculated magnetization curves are quite larger than the experimental data.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011161
    DOI: 10.7566/JPSCP.30.011161

Permalink: https://www.hzdr.de/publications/Publ-30849
Publ.-Id: 30849


Phonon-induced near-field resonances in multiferroic BiFeO₃ thin films at infrared and THz wavelengths

Wehmeier, L.; Nörenberg, T.; de Oliveira, T. V. A. G.; Klopf, J. M.; Yang, S.-Y.; Martin, L. W.; Ramesh, R.; Eng, L. M.; Kehr, S. C.

Multiferroic BiFeO3 (BFO) shows several phonon modes at infrared (IR) to THz energies, which are expected to carry information on any sample property coupled to crystal lattice vibrations. While macroscopic IR studies of BFO are often limited by single-crystal size, scattering-type scanning near-field optical microscopy (s-SNOM) allows for IR thin film spectroscopy of nanoscopic probing volumes with negligible direct substrate contribution to the optical signal. In fact, polaritons such as phonon polaritons of BFO introduce a resonant tip–sample coupling in s-SNOM, leading to both stronger signals and enhanced sensitivity to local material properties. Here, we explore the near-field response of BFO thin films at three consecutive resonances (centered around 5 THz, 13 THz, and 16 THz), by combining s-SNOM with a free-electron laser. We study the dependence of these near-field resonances on both the wavelength and tip–sample distance. Enabled by the broad spectral range of the measurement, we probe phonon modes connected to the predominant motion of either the bismuth or oxygen ions. Therefore, we propose s-SNOM at multiple near-field resonances as a versatile and very sensitive tool for the simultaneous investigation of various sample properties.

Permalink: https://www.hzdr.de/publications/Publ-30848
Publ.-Id: 30848


Low frequency dependent elastic modulus in UCo1-xOsxAl

Kumano, S.; Ishii, I.; Horio, R.; Mizuno, T.; Umeno, T.; Suzuki, D.; Andreev, A. V.; Gorbunov, D.; Yamamura, T.; Suzuki, T.

UCoAl with the hexagonal ZrNiAl-type structure shows an itinerant metamagnetic phase transition at 0.7 T in the magnetic field along the c-axis. Whereas, this compound becomes to undergo a ferromagnetic phase transition in zero field by substituting Os for Co. UCo0.995Os0.005Al exhibits the ferromagnetic phase transition at TC = 8 K. At high temperatures, the temperature dependence of the transverse elastic modulus C44 in UCo0.995Os0.005 Al shows a slight softening below 50 K. The softening turns to an abrupt hardening below 30 K. With further decreasing temperature, a bending is observed at TC. Although TC changes sensitively by applying the magnetic fields, the temperature of the elastic hardening is robust in the magnetic fields. This elastic hardening is not caused by a magnetic origin. We measured ultrasonic frequency dependences of C44 and found that the temperature of the elastic hardening increases with increasing ultrasonic frequency. We propose that this ultrasonic frequency dependence is due to a large amplitude atomic motion of constituent atoms.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011173
    DOI: 10.7566/JPSCP.30.011173

Permalink: https://www.hzdr.de/publications/Publ-30847
Publ.-Id: 30847


Preclinical incorporation dosimetry of [18F]FACH - a novel 18F-labeled MCT1/MCT4 lactate transporter inhibitor for imaging cancer metabolism with PET

Sattler, B.; Kranz, M.; Wenzel, B.; Thachaantara Jain, N.; Moldovan, R.-P.; Toussaint, M.; Deuther-Conrad, W.; Ludwig, F.-A.; Teodoro, R.; Sattler, T.; Sadeghzadeh, M.; Sabri, O.; Brust, P.

Overexpression of monocarboxylate transporters (MCTs) has been shown for a variety of human cancers (e.g. colon, brain, breast, and kidney) and inhibition resulted in intracellular lactate accumulation, acidosis and cell death. Thus, MCTs are promising targets to investigate tumor cancer metabolism with positron emission tomography (PET). Here, the organ doses (OD) and the effective dose (ED) of the first 18F-labeled MCT1/MCT4 inhibitor were estimated in juvenile pigs. Whole-body dosimetry was performed in three piglets (age: ~6 weeks, weight: ~13-15 kg). The animals were anaesthetized and subjected to sequential PET/CT up to 5h after i.v. injection of 156 ± 54 MBq [18F]FACH. All relevant organs were defined by volumes of interest. Exponential curves were fitted to the time-activity data. Time and mass scales were adapted to the human order of magnitude and the ODs calculated using the ICRP 89 adult male phantom with OLINDA 2.1. The ED was calculated using tissue weighting factors as published in the ICRP103. The highest organ dose was received by the urinary bladder (62.6 ± 28.9 µSv/MBq), followed by the gall bladder(50.4 ± 37.5 µSv/MBq) and the pancreas (30.5 ± 27.3 µSv/MBq). The highest contribution to the ED was by the urinary bladder (2.5 ± 1.1 µSv/MBq) followed by the red marrow (1.7 ± 0.3 µSv/MBq) and the stomach (1.3 ± 0.4 µSv/MBq). According to this preclinical analysis,the ED to humans is 12.4 µSv/MBq when applying the ICRP103 tissue weighing factors. Taking into account that preclinical dosimetry underestimates the dose to humans by up to 40%, the conversion factor applied for estimation of the ED to humans would raise to 20.6 µSv/MBq. Resultantly, the ED to humans upon an i.v. application of ~300 MBq [18F]FACH would be about 6.2mSv. This risk assessment encourages to translate [18F]FACH to clinical study phases and to further investigate its potential as a clinical tool for cancer imaging with PET.

Keywords: preclinical radiopharmaceutical dosimetry; [18F]FACH; radiation safety; image based internal dosimetry; OLINDA; MCT1/MCT4 lactate transporter inhibitor

Permalink: https://www.hzdr.de/publications/Publ-30846
Publ.-Id: 30846


Crystal-field effects in Er3RuAl12with a distorted kagome lattice

Gorbunov, D.; Ishii, I.; Kurata, Y.; Andreev, A. V.; Suzuki, T.; Zherlitsyn, S.; Wosnitza, J.

We report on the magnetic and elastic properties of Er3Ru4Al12 in static and pulsed magnetic fields up to 58 T. From the ultrasound results, we obtain evidence for a phase transition at 2 K related to magnetic ordering. Furthermore, in the paramagnetic state, Er3Ru4Al12 shows pronounced anomalies in the magnetization and elastic moduli as a function of temperature and magnetic field. We explain our findings using a crystal-electricfield (CEF) model that includes quadrupolar interactions and propose a CEF level scheme for this material. However, the CEF effects cannot explain all field-induced anomalies, which indicates that refined models are needed for explaining these.

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Permalink: https://www.hzdr.de/publications/Publ-30845
Publ.-Id: 30845


Ultrasonic Dispersion in the Hexagonal Ferromagnet Nd3Ru4Al12

Suzuki, T.; Mizuno, T.; Kumano, S.; Umeno, T.; Suzuki, D.; Andreev, A. V.; Gorbunov, D.; Henriques, M. S.; Ishii, I.

The rare-earth ferromagnet Nd3Ru4Al12 has Curie temperature TC= 39 K and crystallizes in the hexagonal Gd3Ru4Al12-type structure (space group P63/mmc), which is a non-caged structure. A previous measurement of the elastic moduli has shown an upturn around 10 K in the temperature dependence of the longitudinal modulus C33. The upturn is not caused by any phase transition. To investigate the origin of the upturn in Nd3Ru4Al12, we have measured the temperature dependence of C33 at various ultrasonic frequencies. The temperature of the upturn increases with increasing ultrasonic frequency indicating the ultrasonic dispersion, and it does not change under applied magnetic fields. These results suggest that the upturn originates from the rattling effect at one of the aluminium sites in the crystal structure. Assuming a Debye-type relaxation for the elastic modulus and an Arrhenius-type relaxation time for the rattling, the activation energy was estimated as E = 115 K and the relaxation time as Ƭ0 = 1.5 x 10-13s.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011091
    DOI: 10.7566/JPSCP.30.011091

Permalink: https://www.hzdr.de/publications/Publ-30843
Publ.-Id: 30843


Air-side thermal and flow performance study of additively manufactured tube bundle heat exchangers with novel fin design

Unger, S.; Beyer, M.; Pietruske, H.; Szalinski, L.; Hampel, U.

Finned tube bundle heat exchangers are used in a variety of applications with the plain circular fin being the most common design. In the present investigation we proposed two novel heat exchanger designs integrated pins, which improve the heat conduction from the fin base to the fin tip as well as the convective heat transfer along the fin surface. Tubes with conventional circular plain fins (CPF) as well as novel circular integrated pin fins (CIPF) and serrated integrated pin fins (SIPF) were additively generated by a Selective Laser Melting (SLM) process. They were tested in a flow channel in a 2-row and a 3-row configuration under forced convection with Reynolds numbers between 1600 and 6600. For the new SIPF and CIPF designed we found an improved Nusselt number compare to the CPF and higher Nusselt number for the 2-row compared to the 3-row configuration. From the analysis of the single tube rows it was found that the Nusselt number is highest for the first row and reduces downstream. The friction factor was lowest for the SIPF at all Reynolds number and the CIPF gave lower friction factor compared to CPF for Reynolds numbers up to approximately Re=4000. Furthermore, the performance of the heat transfer surface was evaluated by the performance evaluation criterion. Hence, an enhancement of 72.6 % and 33.6 % for the 2-row configuration as well as 63.4 % and 29.1 % for the 3-row configuration for the SIPF and CIPF compared to the CPF was found. The compactness of the heat exchanger was evaluated by the volumetric heat flux density, which was greatest for the CIPF followed by the SIPF and lowest for the conventional CPF design. In general the 2-row heat exchanger configuration reached greater performance and volumetric heat flux density than the 3-row configuration. The global performance criterion strongly depends on the flow conditions. Thus, the SIPF heat exchanger performs best at lower and intermediate Reynolds numbers up to Re=5000 and the CPF design is best at higher Reynolds numbers. Eventually, the surface area and the volume of the heat exchanger with SIPF are 30.7 % and 6.9 % lower compared to the conventional heat exchanger. Based on the experimental results an empirical heat transfer correlation was derived, which includes Nusselt number, Reynolds number, Prandtl number, fin design and tube row number.

Keywords: Novel heat exchanger designs; Heat transfer; Friction factor; Thermal-flow performance; Additive Manufacturing; Integrated pin fin

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Permalink: https://www.hzdr.de/publications/Publ-30842
Publ.-Id: 30842


Thermal and flow performance of tilted oval tubes with novel fin designs

Unger, S.; Beyer, M.; Szalinski, L.; Hampel, U.

We studied the thermal and flow performance of tube heat exchangers with novel fin designs for tube tilt angles of "0°,20°,30°" and "40°" to the horizontal. The novel fin designs target to enhance the conduction heat transfer within the fin and the convective heat transfer along the fin surface simultaneously. Tubes with three different fin designs, the circular plain fin (CPF), the circular integrated pin fin (CIPF) and the serrated integrated pin fin (SIPF), were additively manufactured by selective laser melting and experimentally investigated in an air flow channel for Reynolds number between "1800" and "7800" . We analysed the performance evaluation criterion, the volumetric heat flux density and the global performance criterion. It was found, that the SIPF achieves highest performance evaluation criterion and the CPF performs worst. Thus, the SIPF is recommended, when the required surface area, the material cost and the weight of the finned tube heat exchanger are relevant. Highest heat transfer per volume heat exchanger and temperature difference was achieved for the CIPF at highest tube tilt angle. The value of the global performance criterion strongly depends on the fin design and the tube tilt angle. For the horizontal orientation the CPF reaches highest global performance and for the 40° tube tilt angle the CIPF gives best performance. From the experimental data we derived appropriate heat transfer correlations for Reynolds number, Prandtl number, tube tilt angle and fin designs.

Keywords: Finned tube heat exchanger; Novel fin designs; Heat transfer; Friction factor; Tube tilt angle; Thermal-flow performance; Additive Manufacturing

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Permalink: https://www.hzdr.de/publications/Publ-30841
Publ.-Id: 30841


Air-side thermal and flow performance study of additively manufactred tube bundle heat exchagers with novel fin designs

Unger, S.; Beyer, M.; Pietruske, H.; Szalinski, L.; Hampel, U.

These are the raw data and the processed data of the journal paper "Air-side thermal and flow performance study of additively manufactred tube bundle heat exchagers with novel fin designs".

The raw data contains the measured values on the experimental setup and the processed data contains the data of the data used in the corresponding journal publication.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-03-23
    DOI: 10.14278/rodare.271
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-30840
Publ.-Id: 30840


Rhenium and technetium-complexed silicon rhodamines as near-infrared imaging probes for bimodal SPECT- and optical imaging

Kanagasundaram, T.; Kramer, C. S.; Boros, E.; Kopka, K.

Radiolabelled fluorescent dyes are decisive for bimodal imaging and currently in demand for scintigraphic and optical imaging. This powerful method allows the combination of nuclear imaging (e.g. SPECT-imaging) and optical imaging which leads to synergistic effects, resulting in high spatial resolution and high tissue penetration from the whole body to the subcellular level. The new approaches in tumor imaging and its resection enables the accurate differentiation of healthy and diseased (e.g. tumor) tissues. Organic dyes belonging to the rhodamine family show unique optical properties such as high quantum yields, large extinction coefficients, absorption and emission properties in the optical window. The goal of this work was the development of small molecule near-infrared (NIR) light-emitting silicon-rhodamines (SiR) for scintigraphic and optical imaging. We utilized the dyes for copper(I)-catalyzed alkyne-azide [3+2]-cycloaddition to receive respective 1,2,3-triazoles for complexing the prominent SPECT-radiometal 99mTc(I)- and rheniumtricarbonyl core using the click-to-chelate concept from Mindt et al. The dyes were fully characterized using NMR-, UV/VIS/NIR-spectroscopy, IR and mass spectrometry. The presented silicon rhodamines with optical properties in the near-infrared region with emission wavelengths of ca. 650 nm and quantum yields in aqueous solution of up to 0.10 were received in seven reaction steps. The determined extinction coefficients of ca. 150.000 M-1cm-1 show promising results, making them potentially useful for bimodal imaging. Furthermore the dyes were prepared as precursors for radiolabelling with the SPECT-compatible radiometal technetium-99m. Corresponding rhenium-Si-rhodamines [used as a non-radioactive technetium-surrogate] were chemically characterized as well. Subsequently perfomed radiolabelling experiments have shown radiochemical yields of up to 59% and a radiochemical purity greater than 98%. The complexes show high stability both in aqueous solution and even in challenging experiments with histidine under physiological conditions. The first-in-class dyes have been synthesized to elucidate their potential for fluorescence- and radio-guided surgery. The non-targeted radiolabelled rhodamine dyes are subject of ongoing biological evaluations and the incorporation of biovectors into the dye for selective (tumor) targeting are topics of current research.

Keywords: Radiochemistry; Organic Synthesis; Click Chemistry; Technetium-99m Chemistry; Fluorescent Dyes; Silicon Rhodamines; Bimodal Imaging; Multimodal Imaging; SPECT Imaging; Optical Imaging

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Permalink: https://www.hzdr.de/publications/Publ-30839
Publ.-Id: 30839


The application of HEXS and HERFD XANES for accurate structural characterization of actinide nanomaterials: application to ThO₂.

Amidani, L.; Vaughan, G. B. M.; Plakhova, T. V.; Romanchuk, A. Y.; Gerber, E.; Svetogorov, R.; Weiß, S.; Joly, Y.; Kalmykov, S. N.; Kvashnina, K.

Structural characterization of actinide nanoparticles (NPs) is of primary importance and hard to achieve, especially for non‐homogeneous samples with NPs below 3 nm. By combining High Energy X‐ray Scattering (HEXS) and High‐Energy‐Resolution Fluorescence Detected X‐ray Near‐Edge Structure (HERFD XANES), we characterized for the first time both short‐ and medium‐range order of ThO₂ NPs obtained by chemical precipitation. With this methodology, a novel insight into the structure of NPs at different steps of their formation process is achieved. The Pair Distribution Function (PDF) reveals a high concentration of ThO₂ small units similar to Th hexamer clusters mixed with 1 nm ThO₂ NPs in the initial steps of formation. Drying the precipitates at ⁓150 °C promotes recrystallization of the smallest units into more thermodynamically stable ThO₂ NPs. HERFD XANES at Th M₄ edge, a direct probe of the f states, shows variations that we correlate to the break of the local symmetry around Th atoms, which most likely concerns surface atoms. Together, HEXS and HERFD are a powerful methodology to investigate actinide NPs and their formation mechanism.

Keywords: actinides; HERFD; HEXS; nanoparticles; ThO₂

Permalink: https://www.hzdr.de/publications/Publ-30838
Publ.-Id: 30838


Photoexcited organic molecules en route to highly efficient autoionization

Vempati, S.; Bogner, L.; Richter, C.; Deinert, J.-C.; Foglia, L.; Gierster, L.; Stähler, J.

The conversion of optical and electrical energies in novel materials is key to modern optoelectronic and light-harvesting applications. Here, we investigate the equilibration dynamics of photoexcited 2,7-bis(biphenyl-4-yl)-2′,7′-ditertbutyl-9,9′-spirobifluorene (SP6) molecules adsorbed on ZnO(10-10) using femtosecond time-resolved two-photon photoelectron and optical spectroscopies. We find that, after initial ultrafast relaxation on femtosecond and picosecond time scales, an optically dark state is populated, likely the SP6 triplet (T) state, that undergoes Dexter-type energy transfer (rDex = 1.3 nm) and exhibits a long decay time of 0.1 s. Because of this long lifetime, a photostationary state with average T–T distances below 2 nm is established at excitation densities in the 1020 cm−2 s−1 range. This large density enables decay by T–T annihilation (TTA) mediating autoionization despite an extremely low TTA rate of kTTA = 4.5 ⋅ 10−26 m3 s−1. The large external quantum efficiency of the autoionization process (up to 15%) and photocurrent densities in the mA cm−2 range offer great potential for light-harvesting applications.

Keywords: Autoionization; Photoelectron spectroscopy; organic electronics

Permalink: https://www.hzdr.de/publications/Publ-30837
Publ.-Id: 30837


Drone-based surveys of mineral deposits

Jackisch, R.

Drones are becoming important tools for mineral exploration by contributing to the safe, efficient and sustainable provision of the high-tech metals that are required by modern society.

Keywords: economic geology; mineralogy; UAV; hyperspectral; magnetics

Permalink: https://www.hzdr.de/publications/Publ-30836
Publ.-Id: 30836


UniCAR T cell immunotherapy enables efficient elimination of radioresistant cancer cells

Arndt, C.; Loureiro, L. R.; Feldmann, A.; Jureczek, J.; Bergmann, R.; Máthé, D.; Hegedüs, N.; Berndt, N.; Koristka, S.; Metwasi, N.; Fasslrinner, F.; Lamprecht, C.; Kegler, A.; Hoffmann, A.; Bartsch, T.; Köseer, A. S.; Egan, G.; Schmitz, M.; Hořejší, V.; Krause, M.; Dubrovska, A.; Bachmann, M.

Induction or selection of radioresistant cancer (stem) cells following standard radiotherapy is presumably one of the major causes for recurrence of metastatic disease. One possibility to prevent tumor relapse is application of targeted immunotherapies including e.g. chimeric antigen receptor (CAR) T cells. In light of long-term remissions it is highly relevant to clarify whether radioresistant cancer cells are susceptible to CAR T cell-mediated killing. To answer this question, we evaluated the anti-tumor activity of the switchable universal chimeric antigen receptor (UniCAR) system against highly radioresistant head and neck squamous cell carcinoma cells both in vitro and in vivo. Following specific UniCAR T cell engagement via EGFR or CD98 target modules, T cell effector mechanisms were induced including secretion of pro-inflammatory cytokines, up-regulation of granzyme B and perforin as well as T cell proliferation. CD98- or EGFR-redirected UniCAR T cells further possess the capability to efficiently lyse radioresistant tumor cells. Observed anti-tumor effects were comparable to those against the radiosensitive parental cell lines. Finally, redirected UniCAR T cells significantly inhibited growth of radioresistant cancer cells in immunodeficient mice. Taken together, our obtained data underline that the UniCAR system is able to overcome radio-resistance. Thus, it represents an attractive technology for the development of combined radioimmunotherapeutic approaches that might improve the outcome of patients with metastatic radioresistant tumor diseases.

Keywords: radio-resistance; CD98; EGFR; adaptor CAR; T cell immunotherapy

Permalink: https://www.hzdr.de/publications/Publ-30835
Publ.-Id: 30835


SiPM readout for NeuLAND

Hensel, T.; Weinberger, D.; Bemmerer, D.; R3B Collaboration

Statusreport SiPM readout for NeuLAND

Keywords: NeuLAND; SiPM; R3B

  • Lecture (Conference)
    R3B Collaboration Meeting, 29.10.2019, Darmstadt, Deutschalnd

Permalink: https://www.hzdr.de/publications/Publ-30834
Publ.-Id: 30834


General Colloidal Synthesis of Transition-Metal Disulfide Nanomaterials as Electrocatalysts for Hydrogen Evolution Reaction

Meerbach, C.; Klemmed, B.; Spittel, D.; Bauer, C.; Park, Y. J.; Hübner, R.; Jeong, H. Y.; Erb, D.; Shin, H. S.; Lesnyak, V.; Eychmüller, A.

The material-efficient monolayers of transition-metal dichalcogenides (TMDs) are a promising class of ultrathin nanomaterials with properties ranging from insulating through semiconducting to metallic, opening a wide variety of their potential applications from catalysis and energy storage to optoelectronics, spintronics, and valleytronics. In particular, TMDs have a great potential as emerging inexpensive alternatives to noble metal-based catalysts in electrochemical hydrogen evolution. Herein, we report a straightforward, low-cost, and general colloidal synthesis of various 2D transition-metal disulfide nanomaterials, such as MoS2, WS2, NiSx, FeSx, and VS2, in the absence of organic ligands. This new preparation route provides many benefits including relatively mild reaction conditions, high reproducibility, high yields, easy upscaling, no post-thermal annealing/treatment steps to enhance the catalytic activity, and, finally, especially for molybdenum disulfide nanosheets, high activity in the hydrogen evolution reaction. To underline the universal application of the synthesis, we prepared mixed CoxMo1-xS2 nanosheets in one step to optimize the catalytic activity of pure undoped MoS2, which resulted in an enhanced hydrogen evolution reaction performance characterized by onset potentials as low as 134 mV and small Tafel slopes of 55 mV/dec.

Permalink: https://www.hzdr.de/publications/Publ-30833
Publ.-Id: 30833


Promoting the Electrocatalytic Performance of Noble Metal Aerogels by Ligand-Directed Modulation

Fan, X.; Zerebecki, S.; Du, R.; Hübner, R.; Marzum, G.; Jiang, G.; Hu, Y.; Barcikowki, S.; Reichenberger, S.; Eychmüller, A.

Noble metal aerogels (NMAs) are an emerging class of porous materials. Embracing nano-sized highly-active noble metals and porous structures, they display unprecedented performance in diverse electrocatalytic processes. However, various impurities, particularly organic ligands, are often involved in the synthesis and remain in the corresponding products, hindering the investigation of the intrinsic electrocatalytic properties of NMAs. Here, starting from laser-generated inorganic-salt-stabilized metal nanoparticles, various impurity-free NMAs (Au, Pd, and Au-Pd aerogels) were fabricated. In this light, we demonstrate not only the intrinsic electrocatalytic properties of NMAs, but also the prominent roles played by ligands in tuning electrocatalysis through modulating the electron density of catalysts. These findings may offer a new dimension to engineer and optimize the electrocatalytic performance for various NMAs and beyond.

Keywords: aerogels; electrocatalysis; laser; ligand; noble metals

Permalink: https://www.hzdr.de/publications/Publ-30832
Publ.-Id: 30832


Engineering Multimetallic Aerogels for pH-Universal HER and ORR Electrocatalysis

Du, R.; Jin, W.; Hübner, R.; Zhou, L.; Hu, Y.; Eychmüller, A.

The advent of noble metal aerogels (NMAs), that feature the high catalytic activity of noble metals and unique structural attributes of aerogels, has stimulated research on a new class of outstanding electrocatalysts. However, limited by the available compositions, the explored electrocatalytic reactions on NMAs are highly restricted and certain important electrochemical processes have not been investigated. Here, an effective gelation approach is demonstrated by using a strong salting-out agent (i.e., NH4F), thereby expanding the composition of NMAs to various multimetallic systems and providing a platform to investigate composition-dependent electrocatalytic performance of NMAs. Combining structural features of aerogels and optimized chemical compositions, the Au-Pt and Au-Rh aerogel catalysts manifest remarkable pH-universal (pH = 0-14) performance surpassing commercial Pt/C and many other nanoparticle (NP)-based catalysts in the electrocatalytic oxygen reduction reaction, hydrogen evolution reaction, and water splitting, displaying enormous potential for the electrochemical hydrogen production, fuel cells, etc.

Keywords: electrocatalysis; hydrogen evolution reaction; metal aerogels; oxygen reduction reaction; pH

Permalink: https://www.hzdr.de/publications/Publ-30831
Publ.-Id: 30831


Tomographic imaging of two-phase flow

Hampel, U.; Barthel, F.; Bieberle, A.; Bieberle, M.; Boden, S.; Franz, R.; Neumann-Kipping, M.; Tas-Köhler, S.

Two-phase flow is to be found in many situations of nuclear reactor operation and accident sequences. Examples are loss of coolant accidents and boiling in fuel assemblies. Hence, mod-elling of two-phase flow is a primary concern in nuclear safety research. Model development and code validation frequently require experimental data, preferably taken under plant ther-mal-hydraulic conditions. Tomographic imaging techniques provide a way to analyze two-phase flow with high spatial resolution. In this paper we introduce recent developments in X-ray tomography and its application to three different problems related to nuclear safety.

Keywords: two-phase flow; core thermal hydraulics; tomography; steam condensation; boiling

Permalink: https://www.hzdr.de/publications/Publ-30830
Publ.-Id: 30830


Bipolar spin Hall nano-oscillators

Hache, T.; Li, Y.; Weinhold, T.; Scheumann, B.; Trindade Goncalves, F. J.; Hellwig, O.; Faßbender, J.; Schultheiß, H.

We demonstrate a novel type of spin Hall nano-oscillators (SHNOs) that allow for efficient tuning of magnetic auto-oscillations over an extended range of gigahertz frequencies, using bipolar direct currents at constant magnetic elds. This is achieved by stacking two distinct magnetic materials with a platinum layer in between. In this device, the orientation of the spin polarised electrons accumulated at the top and bottom interfaces of platinum is switched upon changing the polarity of the direct current. As a result, the effective anti-damping required to drive large amplitude auto-oscillations can appear either at the top or bottom magnetic layer. Tuning of the auto-oscillation frequencies by several gigahertz can be obtained by combining two materials with sufficiently different saturation magnetization. Here we show that the combination of NiFe and CoFeB can result in 3 GHz shifts in the auto-oscillation frequencies. Bipolar SHNOs as such may bring enhanced synchronisation capabilities to neuromorphic applications.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-03-18
    DOI: 10.14278/rodare.269
    License: CC-BY-4.0

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-30829
Publ.-Id: 30829


Round robin into best practices for the determination of indentation size effects

Ruiz-Moreno, A.; Hähner, P.; Kurpaska, L.; Jagielski, J.; Spätig, P.; Trebala, M.; Hannula, S.-P.; Merino, S.; de Diego, G. . .; Namburi, H.; Libera, O.; Terentyev, D.; Khvan, T.; Heintze, C.; Jennett, C.

The paper presents a statistical study of nanoindentation results obtained in seven European laboratories which have joined a round robin exercise to assess methods for the evaluation of indentation size effects. The study focuses on the characterization of ferritic/martensitic steels T91 and Eurofer97, envisaged as structural materials for nuclear fission and fusion applications, respectively. Depth-controlled single cycle measurements at various final indentation depths, force-controlled single cycle and force-controlled progressive multi-cycle measurements using Berkovich indenters at room temperature have been combined to calculate the indentation hardness and the elastic modulus as a function of depth applying the Oliver and Pharr method. Intra- and inter-laboratory variabilities have been evaluated. Elastic modulus corrections have been applied to the hardness data to compensate for materials related systematic errors, like pile-up behaviour, which is not accounted for by the Oliver and Pharr theory, and other sources of instrumental or methodological bias. The correction modifies the statistical hardness profiles and allows determining more reliable indentation size effects.

Permalink: https://www.hzdr.de/publications/Publ-30828
Publ.-Id: 30828


Rethinking ore sorting - The search for the optimal sensor

Kern, M.; Tusa, L.; Khodadadzadeh, M.; Leißner, T.; Gloaguen, R.; van den Boogaart, K. G.; Gutzmer, J.

Zusammenfassung: Sensorgestützte Sortierung ist eine Technologie, die in zunehmendem Maße zur Aufbereitung von Primärrohstoffen verwendet wird. Mit dem hier vorgestellten simulations-basierten Ansatz ist es möglich, den optimalen Sensor durch quantitative Analysen der Mineralogie und Datenverwertung in Kombination mit Maschinellem Lernen (ML) gezielt zu bestimmen. Dieses Vorgehen ist generisch und kann auf viele Rohstofftypen angepasst werden. Darüber hinaus birgt das Vorgehen das Potenzial, eine Schlüsseltechnologie zur Optimierung von Aufbereitungsprozessen zu werden.

Summary: Sensor-based sorting is a technology which is increasingly used for processing primary raw materials. With the simulation-based approach presented in this paper, it is possible to specifically determine the optimal sensor based on quantitative analyses of the mineralogy and data utilization in combination with machine learning (ML). This approach is generic and can be adapted to many types of raw material. Moreover, the approach has the potential to become a key technology for the optimization of processing operations.

  • AT Minerals Processing 61(2020)3, 54-64

Permalink: https://www.hzdr.de/publications/Publ-30826
Publ.-Id: 30826


Pilot-scale investigation of two Electric Pulse Fragmentation (EPF) approaches for the mineral processing of a low-grade cassiterite schist ore

Bru, K.; Sousa, R.; Machado Leite, M.; Broadbent, C.; Stuart, G.; Pashkevich, D.; Kern, M.; Parvaz, D. B.

Two approaches for the use of the Electric Pulse Fragmentation (EPF) in the beneficiation of a low-grade cassiterite schist ore were investigated through pilot-scale tests performed on samples of about 270 kg. The first approach used EPF treatment for pre-concentration while in the second approach the EPF technology was mostly used for crushing. Comparison with the use of conventional crushers was performed.
Results showed that the EPF pre-treatment led to a decrease of the Bond rod mill work index while the Bond ball mill work index remained unchanged. This means that the decrease in the energy consumption requested to grind the material down to 1.18 mm (closing screen of the Bond rod mill work index) is no longer noticeable with additional grinding stage to reach a size down to 106 μm (closing screen of the Bond ball mill work index).
This may be due to the fracture network generated during EPF being consumed immediately in the subsequent comminution step. Alternatively, it may be that the Bond ball mill work index is not appropriate for exhibiting the weakening effect of the EPF technology when the mineral liberation size is coarser than the closing screen size used for the test. Concentration tests performed on the sample treated with the first approach for EPF showed no marked change in separation performance. However, a higher concentrate grade was obtained when using this EPF pre-treatment, indicating a probable potential for improvement.

Keywords: Cassiterite; Electric Pulse Fragmentation; Selective comminution; Pre-concentration

Permalink: https://www.hzdr.de/publications/Publ-30825
Publ.-Id: 30825


The effect of noise on the synchronization dynamics of the Kuramoto model on a large human connectome graph

Ódor, G.; Kelling, J.; Deco, G.

We have extended the study of the Kuramoto model with additive Gaussian noise running on the KKI-18 large human connectome graph. We determined the dynamical behavior of this model by solving it numerically in an assumed homeostatic state, below the synchronization crossover point we determined previously. The desynchronization duration distributions exhibit power-law tails, characterized by the exponent in the range 1.1 < τt < 2, overlapping the in vivo human brain activity experiments by Palva et al. We show that these scaling results remain valid, by a transformation of the ultra-slow eigen-frequencies to Gaussian with unit variance.
We also compare the connectome results with those, obtained on a regular cube with N = 106 nodes, related to the embedding space, and show that the quenched internal frequencies themselves can cause frustrated synchronization scaling in an extended coupling space.

Keywords: Frustrated Synchronization; Human Connectome; Chimera states; Noisy Kuramoto; Criticality in resting state

Permalink: https://www.hzdr.de/publications/Publ-30824
Publ.-Id: 30824


Contemporary Synthesis of Ultrasmall (sub-10 nm) Upconverting Nanomaterials

Joshi, T.; Mamat, C.; Stephan, H.

Due to their unique photophysical properties, upconverting nanoparticles (UCNPs), i.e. particles capable of converting near-infrared (NIR) photons into tunable emissions in the range of ultraviolet (UV) to NIR, have great potential for use in various biomedical fields such as bioimaging, photodynamic therapy and bioanalytical applications. As far as biomedical applications concerned, these materials have a number of advantageous properties such as brilliant luminescence and exceptional photo-stability. Very small “stealth” particles (sub-10 nm), which can circulate in the body largely undetected by the immune system, are particularly important for in vivo use. The fabrication of such particles, which simultaneously have a defined (ultrasmall) size and the required optical properties, is a great challenge and an area that is in its infancy. This minireview provides a concise overview of recent developments on appropriate synthetic methodologies to produce such UCNPs. Particular attention was given to the influence of both surfactants and dopants used to precisely adjust size, crystalline phase and optical properties of UCNPs.

Keywords: Lanthanides; Nanomaterials; Synthesis; Ultrasmall; Upconversion

Permalink: https://www.hzdr.de/publications/Publ-30823
Publ.-Id: 30823


Bipolar spin Hall nano-oscillators

Hache, T.; Li, Y.; Weinhold, T.; Scheumann, B.; Trindade Goncalves, F. J.; Hellwig, O.; Faßbender, J.; Schultheiß, H.

We demonstrate a novel type of spin Hall nano-oscillators (SHNOs) that allow for efficient tuning of magnetic auto-oscillations over an extended range of gigahertz frequencies, using bipolar direct currents at constant magnetic fields. This is achieved by stacking two distinct magnetic materials with a platinum layer in between. In this device, the orientation of the spin polarised electrons accumulated at the top and bottom interfaces of platinum is switched upon changing the polarity of the direct current. As a result, the effective anti-damping required to drive large amplitude auto-oscillations can appear either at the top or bottom magnetic layer. Tuning of the auto-oscillation frequencies by several gigahertz can be obtained by combining two materials with suffciently different saturation magnetization. Here we show that the combination of NiFe and CoFeB can result in 3 GHz shifts in the auto-oscillation frequencies. Bipolar SHNOs as such may bring enhanced synchronisation capabilities to neuromorphic applications.

Keywords: magnetism; spin Hall; nano-oscillator; auto-oscillations; bipolar; oscillator; nanofabrication; microwave; high-frequency

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Permalink: https://www.hzdr.de/publications/Publ-30822
Publ.-Id: 30822


Structure variations within RSi2 and R2TSi3 silicides. Part I. Structure overview

Nentwich, M.; Zschornak, M.; Sonntag, M.; Gumeniuk, R.; Gemming, S.; Leisegang, T.; Meyer, D. C.

Here, structural parameters of various structure reports on RSi2 and R2TSi3 compounds [where R is an alkaline earth metal, a rare earth metal (i.e. an element of the Sc group or a lathanide), or an actinide and T is a transition metal] are summarized. The parameters comprising composition, lattice parameters a and c, ratio c/a, formula unit per unit cell and structure type are tabulated. The relationships between the underlying structure types are presented within a group–subgroup scheme (Bärnighausen diagram). Additionally, unexpectedly missing compounds within the R2TSi3 compounds were examined with density functional theory and compounds that are promising candidates for synthesis are listed. Furthermore, a correlation was detected between the orthorhombic AlB2-like lattices of, for example, Ca2AgSi3 and the divalence of R and the monovalence of T. Finally, a potential tetragonal structure with ordered Si/T sites is proposed.

Keywords: silicide; lanthanide; ordering phenomena; structure prediction; DFT

Permalink: https://www.hzdr.de/publications/Publ-30821
Publ.-Id: 30821


Horizontal annular flow through orifice studied by X-ray microtomography

Porombka, P.; Boden, S.; Lucas, D.; Hampel, U.

A mobile X-ray microtomography (µCT) system was developed which enables 3D scanning of horizontal and vertical test sections. The µCT system has been applied to measure the local, time-averaged volume fraction distribution of developing annular air-water flow in a horizontal pipe with µm spatial resolution. Based on the volume fraction data the liquid film thickness profile is computed and the accumulation, stripping and renewal of the annular liquid film at a circular orifice is studied. The development length of the annular flow downstream of the orifice is evaluated based on the integral volume fraction and the change of the film thickness profile along the pipe axis. Both parameters give a consistent result, indicating that liquid film renewal can be judged based on integral measurement techniques in this case. The detailed 3D data is intended for validation of computational fluid dynamics codes based on phase-averaged variables such as the Euler-Euler approach.

Keywords: X-ray microtomography; film thickness; circular orifice; annular flow

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Permalink: https://www.hzdr.de/publications/Publ-30820
Publ.-Id: 30820


Novel cosmogenic datings in landslide deposits, San Juan, Argentina

Jeanneret, P.; Moreiras, S. M.; Merchel, S.; Gärtner, A.; Binnie, S.; Orgeira, M. J.; Aumaître, G.; Bourlès, D.; Keddadouche, K.

High-mountain environments in an active tectonic setting are prone to landsliding. The triggering mechanisms are still a challenge as these areas are influenced by several pre-conditioning factors coupled with active seismicity and climatic forcings. Understanding the intrinsic and external mechanisms in which these events are influenced would help to establish better constraints onto their timing and periodicity and, eventually, hazard assessment and prediction. Glacially eroded valleys are especially prone as they deeply incise mountain ranges leaving unstable slopes once they retreat. Establishing the timing of such events enables to link the causality and comprehend in a deeper level the triggering and pre-conditioning factors of landslides. To this aim, ¹⁰Be and ²⁶Al cosmogenic age determinations were performed in three landslide deposits in a poorly studied area of San Juan province, all of which are novel to the area. Coupled with remote sensing techniques, field observations and detailed stratigraphic and sedimentological studies, these new large landslides represent a first approach to understand this dynamic environment. The three landslides were categorized as rock avalanches found in the middle and lower reaches of the Blanco River, sourced from the Choiyoi Group with evidence of hydrothermal alteration and including/deforming moraine deposits during their fall. Ages range from 20.9±1.4, 10.8±0.7 and 12.8±0.9 ka from the lowermost deposit to the highest, respectively. Even though one sample per deposit is not enough to have statistically significant exposure ages, these values, along with the established chronostratigraphy, allow first order assumptions on the link between deglaciation processes and readjustment of the slopes via large landslide events.

Keywords: Landslide; chronostratigraphy; Arid Central Andes; Argentina

  • Contribution to proceedings
    5th World Landslide Forum, 02.-06.11.2020, Kyoto, Japan
    Understanding and Reducing Landslide Disaster Risk. WLF 2020. ICL Contribution to Landslide Disaster Risk Reduction, Cham: Springer, 978-3-030-60318-2, 361-370
    DOI: 10.1007/978-3-030-60319-9_40

Permalink: https://www.hzdr.de/publications/Publ-30819
Publ.-Id: 30819


Grundlegende F&E-Arbeiten zu Methoden der Zustandsüberwachung von Transport- und Lagerbehältern für abgebrannte Brennelemente und wärmeentwickelnde hochradioaktive Abfälle bei verlängerter Zwischenlagerung

Wagner, M.; Rachamin, R.; Fiß, D.; Schmidt, S.; Reinicke, S.; Kratzsch, A.; Hampel, U.

Mit der verlängerten Zwischenlagerung von abgebrannten Brennelementen ergeben sich verschie-dene regulatorische und sicherheitstechnische Fragestellungen. Eine davon ist die nach der Lang-zeitintegrität der Brennelemente in den Trockenlagerbehältern. Ihre Beantwortung hat direkte Relevanz für den späteren Transport zum Endlager und die Umladung des abgebrannten Kernbrennstoffs in andere Behälter. In dem Verbundvorhaben untersuchten die TU Dresden und die Hochschule Zittau/Görlitz Potenziale und Grenzen von nichtinvasiven Verfahren zur Überwachung des Zustands des radioaktiven Inventars von Trockenlagerbehältern. Als solche wurden Thermographie, strahlungsbasierte Messverfahren sowie akustische Messverfahren betrachtet. Für diese erfolgte eine Bewertung der Empfindlichkeit und Nachweisgrenzen mittels numerischer Simulationen und Durchführung von Experimenten an skalierten Behältermodellen. Es stellte sich heraus, dass insbesondere die Myonenbildgebung und die Analyse der Gamma- und Neutronenstrahlungsfelder am Behälter für ein Überwachungskonzept geeignet sind. Mit diesen Verfahren können Brennstoffverlagerungen ortsaufgelöst detektiert werden.

Keywords: Zwischenlagerung; nicht-invasive Überwachung

  • Other report
    -: -, 2020

Permalink: https://www.hzdr.de/publications/Publ-30818
Publ.-Id: 30818


The influence of negatively charged silica nanoparticles on the surface properties of anionic surfactants: electrostatic repulsion or the effect of ionic strength?

Eftekhari, M.; Schwarzenberger, K.; Javadi, A.; Eckert, K.

The presence of negatively charged nanoparticles affects the surface activity of anionic surfactants in an aqueous phase. Recent studies suggest that electrostatic repulsive forces play an important role in increasing the surface activity of surfactants. However, the addition of nanoparticles also increases the ionic strength of the system, which has a significant impact on the surfactant's properties, e.g. its critical micelle concentration (CMC). To investigate how and to what extent electrostatic forces and ionic strength influence the behavior of ionic surfactants, the surface tension and elasticity of different solutions were measured using drop profile tensiometry as a function of the surfactant (SDBS), nanoparticle (silica) and salt (KNO3) concentration. It is observed that the surface activity of the surfactants is mainly influenced by the change in the system's ionic strength due to the presence of nanoparticles. Several characteristic parameters including the equivalent concentration of the surfactant, the CMC and the apparent partial molar area of the adsorbed surfactant are theoretically calculated and further employed to validate experimental observations. Both the nanoparticles and electrolyte decrease the CMC, while the equivalent concentration of the surfactant remains nearly constant. This paper presents a criterion to estimate the possible influence of such forces for nanoparticles of different sizes and mass fractions.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-30817
Publ.-Id: 30817


Influence of finite temperature Exchange-Correlation effects in Hydrogen

Ramakrishna, K.; Dornheim, T.; Vorberger, J.

We use density functional molecular dynamics (DFT-MD) to study the effect of finite temperature exchange-correlation (xc) in Hydrogen. Using the Kohn-Sham approach, the xc energy of the system, $E_{xc}(r_{s})$ is replaced by the xc free energy $f_{xc}(r_{s},\theta)$ within the local density approximation (LDA) based on parametrized path integral Monte Carlo (PIMC) data for the uniform electron gas (UEG) at warm dense matter (WDM) conditions. We observe insignificant changes in the equation of state (EOS) at the region of metal-insulator transition compared to the regular LDA form, whereas significant changes are observed for T>10000 K, i.e., in the important WDM regime. Thus, our results further corroborate the need for temperature-dependent xc functionals for DFT simulations of WDM systems. Moreover, we present the first finite-temperature DFT results for the EOS of Hydrogen in the electron liquid regime up to $r_{s}=14$ and find a drastic impact (the EOS changes by more than 20%) of thermal xc effects, which manifests at lower temperatures compared to WDM. We expect our results to be important for many applications beyond DFT, like quantum hydrodynamics and astrophysical models.

Keywords: Computational Physics; Plasma Physics; Warm dense matter

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Permalink: https://www.hzdr.de/publications/Publ-30815
Publ.-Id: 30815


Evidence for an Fulde-Ferrell-Larkin-Ovchinnikov State with Segmented Vortices in the BCS-BEC-Crossover Superconductor FeSe

Kasahara, S.; Sato, Y.; Licciardello, S.; Culo, M.; Arsenijevic, S.; Ottenbros, T.; Tominaga, T.; Böker, J.; Eremin, I.; Shibauchi, T.; Wosnitza, J.; Hussey, N. E.; Matsuda, Y.

We present resistivity and thermal-conductivity measurements of superconducting FeSe in intense magnetic fields up to 35 Tapplied parallel to the ab plane. At low temperatures, the upper critical field μ0Hab c2 shows an anomalous upturn, while thermal conductivity exhibits a discontinuous jump at μ0H* ≈ 24 T well below μ0Hab c2, indicating a first-order phase transition in the superconducting state. This demonstrates the emergence of a distinct field-induced superconducting phase. Moreover, the broad resistive transition at high temperatures abruptly becomes sharp upon entering the high-field phase, indicating a dramatic change of the magnetic-flux properties.We attribute the high-field phase to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, where the formation of planar nodes gives rise to a segmentation of the flux-line lattice. We point out that strongly orbital-dependent pairing as well as spin-orbit interactions, the multiband nature, and the extremely small Fermi energy are important for the formation of the FFLO state in FeSe.

Permalink: https://www.hzdr.de/publications/Publ-30814
Publ.-Id: 30814


Spin-dimer ground state driven by consecutive charge and orbital ordering transitions in the anionic mixed-valence compound Rb4O6

Knaflic, T.; Jeglic, P.; Komelj, M.; Zorko, A.; Biswas, P. K.; Ponomaryov, O.; Zvyagin, S.; Reehuis, M.; Hoser, A.; Geiß, M.; Janek, J.; Adler, P.; Felser, C.; Jansen, M.; Arcon, D.

Recently, a Verwey-type transition in the mixed-valence alkali sesquioxide Cs4O6 was deduced from the charge ordering of molecular peroxide O2− 2 and superoxide O 2 anions accompanied by the structural transformation and a dramatic change in electronic conductivity [Adler et al., Sci. Adv. 4, eaap7581 (2018)]. Here, we report that in the sister compound Rb4O6, a similar Verwey-type charge ordering transition is strongly linked to O 2 orbital and spin dynamics. On cooling, a powder neutron diffraction experiment reveals a charge ordering and a cubic-to-tetragonal transition at TCO = 290 K, which is followed by a further structural instability at Ts = 92 K that involves an additional reorientation of magnetic O 2 anions. Magnetic resonance techniques supported by density functional theory computations suggest the emergence of a peculiar type of π*-orbital ordering of the magnetically active O 2 units, which promotes the formation of a quantum spin state composed of weakly coupled spin dimers. These results reveal that as in 3d transition-metal compounds, also in the π* open-shell alkali sesquioxides the interplay between Jahn-Teller-like electron-lattice coupling and Kugel-Khomskii-type superexchange determines the nature of orbital ordering and the magnetic ground state.

Permalink: https://www.hzdr.de/publications/Publ-30813
Publ.-Id: 30813


Strongly coupled electron liquid: Ab initio path integral Monte Carlo simulations and dielectric theories

Dornheim, T.; Sjostrom, T.; Tanaka, S.; Vorberger, J.

The strongly coupled electron liquid provides a unique opportunity to study the complex interplay of strong coupling with quantum degeneracy effects and thermal excitations. To this end, we carry out extensive ab initio path integral Monte Carlo (PIMC) simulations to compute the static structure factor, interaction energy, density response function, and the corresponding static local field correction in the range of 20≤rs≤100 and 0.5≤θ≤4. We subsequently compare these data to several dielectric approximations and find that different schemes are capable to reproduce different features of the PIMC results at certain parameters. Moreover, we provide a comprehensive data table of interaction energies and compare those to two recent parametrizations of the exchange-correlation free energy, where they are available. Finally, we briefly touch upon the possibility of a charge-density wave. The present study is complementary to previous investigations of the uniform electron gas in the warm dense matter regime and, thus, further completes our current picture of this fundamental model system at finite temperature. All PIMC data are available online.

Keywords: warm dense matter; electron liquid; dielectric theory; quantum monte carlo; local field correction; ab initio

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Permalink: https://www.hzdr.de/publications/Publ-30812
Publ.-Id: 30812


Radiopharmaceutical Sciences

Ermert, J.; Benešová, M.; Hugenberg, V.; Gupta, V.; Spahn, I.; Pietzsch, H.-J.; Liolios, C.; Kopka, K.

Clinical Nuclear Medicine, 2nd ed., Chapter 2 Radiopharmaceutical Sciences
Abstract: Chapter 2 Radiopharmaceutical Sciences
Chapter 2 elucidates the field Radiopharmaceutical Sciences from the perspective of its clinical relevance. Radiopharmaceutical Sciences summarize all scientific aspects comprising chemistry, physics and biology/pharmacology that deal with incorporating a suitable radionuclide into a pharmaceutical or other biologically active molecule or molecular entity. The resulting radiopharmaceuticals are used in Nuclear Medicine applications both for diagnosis [meaning non-invasive scintigraphic imaging] and for internal radiotherapy. Internal radiotherapy is nowadays called radioligand therapy (RLT) or endoradiotherapy and altogether is summarized under the term radiothera(g)nostics.
To transfer Radiopharmaceutical Sciences into Clinical Nuclear Medicine first of all radionuclides with corresponding decay characteristics are demanded making these suitable for diagnostic or therapeutic applications. Depending on the short physical half-lives of the radionuclides fast and efficient radiolabeling strategies are required that can be also transferred into the GMP-compliant production of radiopharmaceuticals.
The major challenges in the development of a new radiopharmaceuticals include i.a. the identification of an adequate ligand that specifically binds to the biological target of interest, the chemical modification of the ligand to enable radiolabeling while preserving the binding affinity to the biological target, and the translation of the preclinical evaluations into first in-human studies.
In summary this chapter summarises in a concise manner the current status of clinically relevant radionuclides, SPECT and PET tracers as well as the introduced thera(g)nostic classes of radiopharmaceuticals through the eyes of eight representative radiopharmaceutical scientists.

  • Book chapter
    Ahmadzadehfar H, Biersack HJ, Freeman LM, Zuckier LS: Clinical Nuclear Medicine – 2nd edition, Springer Nature Switzerland AG: Springer International Publishing, 2020, 978-3-030-39455-4, 49-191
    DOI: 10.1007/978-3-030-39457-8

Permalink: https://www.hzdr.de/publications/Publ-30811
Publ.-Id: 30811


Transmission helium ion imaging and time-of-flight spectroscopy

Mousley, M.; Bouton, O.; Klingner, N.; Serralta Hurtado De Menezes, E.; Hlawacek, G.; Eswara, S.; Wirtz, T.

Helium ions are alternative imaging probes to electrons, offering lower de Broglie wavelengths at the same energies and the possibility for different contrast mechanisms [1] [2][3]. A prototype Transmission Helium Ion Microscope (THIM) has been constructed at the Luxembourg Institute of Science and Technology (LIST) [4]. The use of post sample deflection allows the detection of the transmitted ions and neutrals or neutrals only (Figure 1 A). The source is a duo plasmatron with a spot size on the sample of approximately 100 µm and a beam current between 0.1-2nA. There are 2 Einzel lenses and 3 XY deflectors along the column to guide the beam. A MCP detector behind the sample can be used in one of 4 different output mechanisms. Firstly a phosphor screen can be used to produce a transmission helium ion image (THIM) directly which can be captured by an external CCD. Secondly, an anode plate can be used to collect the current directly whilst the beam is scanned, the current recorded at each pixel can then form a scanning image (STHIM). Thirdly, fast electronics are used to blank the beam and provide the start signal for time of flight (TOF) measurements, whilst the anode signal can be used as the stop signal [5]. This allows the generation of TOF-STHIM data. Finally, a delay line detector (DLD) can be placed behind the MCP, from which location and time of flight, of individual particles, can be recorded simultaneously, producing energy spectra and images at the same time. The prototype can image in different modes, THIM , STHIM (scanning THIM), THIM TOF and STHIM TOF. When scanning the beam a secondary electron image can be recorded at the same time (Figure 1 B). In THIM mode the formation of spot patterns due to sample charging was seen when imaging insulating inorganic crystal samples with a stationary broad beam. This was found to be due to unexpectedly large sample charging. We will present preliminary TOF spectra for the transmitted helium ion signal recorded with an anode plate detector and a position sensitive delay line detector. Images formed from different time windows from the TOF spectra show different contrast (Figure 2B) and the spectra for a single layer graphene sample showed increased counts after the main peak (Figure 3), indicative of processes causing energy loss.

[1] Scipioni,L.;, Sanford,C. A.;, Notte,J.;, Thompson,B.;, McVey,S.;, J. Vac. Sci. Technol. B Microelectron. Nanom. Struct., 2009, vol. 27, no. 6, p. 3250, 10.1116/1.3258634.
[2] Kavanagh,K. L.;, Herrmann,C.;, Notte,J. A.;, J. Vac. Sci. Technol. B, Nanotechnol. Microelectron. Mater. Process. Meas. Phenom., 2017, vol. 35, no. 6, p. 06G902, 10.1116/1.4991898.
[3] Wirtz,T.;, De Castro,O.;, Audinot,J.-N.;, Philipp,P.;, Annu. Rev. Anal. Chem., 2019, vol. 12, no. 1, 10.1146/annurev-anchem-061318-115457.
[4] Mousley,M.;, Eswara,S.;, De Castro,O.;, Bouton,O.;, Klinger,N.;, Koch,C. T.;, Hlawacek,G.;, Wirtz,T.;, Submitt. to MRS Commun., vol. 1, pp. 1–10.
[5] Klingner,N.;, Heller,R.;, Hlawacek,G.;, Borany,J. von;, Notte,J.;, Huang,J.;, Facsko,S.;, Ultramicroscopy, 2016, vol. 162, pp. 91–97, 10.1016/j.ultramic.2015.12.005.

Figure 1: A) transmission images formed with ions and neutrals of a copper grid with a single layer graphene membrane pitch 85µm (31µm bar 54µm hole). B) Secondary electron and transmission ion images recorded concurrently in scanning mode.

Figure 2: A) The effect of offsetting the beam aperture on zero loss peak width B) STHIM images, of a 200 mesh copper grid, formed from two different peaks in the TOF spectrum.

Figure 3: The TOF spectrum for a single layer graphene sample on a 300 mesh copper grid, shows extra peaks compared to a background spectrum without a sample.

  • Lecture (Conference) (Online presentation)
    European Microscopy Congress 2020, 23.-28.08.2020, Copenhagen, Denmark

Permalink: https://www.hzdr.de/publications/Publ-30810
Publ.-Id: 30810


Correlative high resolution microscopy and mass spectrometry for morphological and chemical analysis of nanoparticles in biological systems

Biesemeier, A.; de Castro, O.; Serralta Hurtado De Menezes, E.; Klingner, N.; Hlawacek, G.; Gnauck, P.; Duarte Pinto, S.; Lucas, F.; Bebeacua, C.; Cambier, S.; Wirtz, T.

Combined morphological and chemical analysis of ultrastructures is gaining more and more attention in both material and life sciences. Especially the detection of nanoparticles within biological tissue has become a hot topic in environmental research, ecology, nanotoxicology, but also medicine and life science using nanoparticles as carriers for therapeutic drugs. Usually, several highly specialised instruments have to be used to investigate the respective key features of the sample.
Here, a new prototype instrument is presented that combines sub20nm SIMS on a helium ion microscope [HIM; 1] with dark and bright field imaging in one tool – the npSCOPE [2]: the multi-modal instrument couples a Gas Field Ion Source (GFIS) as primary ion beam source with a secondary ion mass spectrometer (SIMS) system featuring a continuous focal plane detector (FPD) and a STHIM detector for imaging the transmitted helium beam. The latter allows investigation of thin samples like biological tissue sections. For morphological/topographical analysis of charging and non-charging bulk samples with sub-nm resolution, the instrument is also equipped with a secondary electron detector and a flood gun. This setup allows (a) higher sensitivity than analytical electron microscopy combined with (b) better spatial resolution than available with other SIMS methodologies typically used for life science questions. The FPD yields a full mass spectrum per scanned pixel featuring the possibility of post hoc analysis of all elements/ion species detected.
Several examples will be presented to show how thin tissue sections can first be investigated with transmitted ions for proper contrast of biological membranes followed by chemical characterization of associated or ingested nanoparticles without the need to transfer samples between different instruments. Specific localisation of the nanoparticles outside the cell membrane or within the cytoplasm or subcellular compartments can be obtained.

In summary, a unique tool for all-in-one physico-chemical characterisation of nanoparticles both before contact to a living organism and after incorporation is presented. Pixel by pixel correlation of the different datasets are directly obtained by image fusion or co-registration methods. For future analysis of frozen-hydrated samples, a cryo-stage is currently being integrated into the npSCOPE. It will yield close to native chemical analysis of diagnostic, environmental and nanotoxicology samples with decreased experiment times and without artefacts due to sample transfer.
References:
[1] T. Wirtz, O. De Castro, J.-N. Audinot, P. Philipp. Imaging and analytics on the Helium Ion Microscope. Annual Review of Analytical Chemistry 12 (2019) 523-543

[2] This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement No. 720964.

Keywords: helium ion microscope; secondary ion mass spectrometer; scanning transmission ion microscopy

  • Lecture (Conference) (Online presentation)
    European Microscopy Congress 2020, 23.-28.08.2020, København, Danmark

Permalink: https://www.hzdr.de/publications/Publ-30809
Publ.-Id: 30809


npSCOPE: A new instrument combining SIMS imaging, SE imaging and transmission ion microscopy for high resolution in-situ correlative investigations

de Casto, O.; Biesemeier, A.; Serralta Hurtado De Menezes, E.; Klingner, N.; Hlawacek, G.; Gnauck, P.; Duarte Pinto, S.; Lucas, F.; Bebeacua, C.; Witrz, T.

In various research areas ranging from materials science to life sciences it becomes more and more important to be able to analyze the structure as well as the chemical composition at the nano-scale. For example, the size of electronic components becomes smaller and smaller increasing the need of having techniques to precisely follow dopant distributions with high spatial resolution. In the field of renewable energy devices, e.g. solar cells and batteries, the performance typically depends on the chosen material composition and distribution. Linking the underlying structure and composition at the nano-scale to the device’s performance is therefore of utmost importance [1,2]. Similar needs for having high spatial resolution and high-sensitivity chemical information can be found in life sciences [3]. In nano-toxicology for instance, it is important to be able to reveal sub-cellular structures and simultaneously determine their chemical, elemental or isotopic composition in order to better understand relevant processes [4]. In most of the afore mentioned studies a number of different instruments is nowadays used to perform these investigations using correlative approaches. Being able to do such correlative studies in one single instrument is definitely beneficial for reducing the analysis time, speeding up the throughput as well as for facilitating the precise localization of the region of interests on the investigated samples.
Therefore, we developed a multimodal nano-analytical platform allowing in-situ analysis of a same sample using different information channels. The instrument is equipped with the ultra-high resolution Gas Field Ion Source (GFIS) technology [5] allowing the sample to be irradiated with very finely focused He+ and Ne+ primary ion
beams. This allows sub-nanometer spatial resolution when working with the secondary electron (SE) detection mode as imaging mode. Furthermore, the instrument incorporates a compact secondary ion mass spectrometer (SIMS) for chemical analysis of samples with excellent sensitivity and high dynamic range. The mass spectrometer is based on a double focusing magnetic sector design and allows sub-20 nm chemical imaging resolution [6-8]. Moreover, the SIMS system incorporates a new kind of detector for parallel mass detection providing a full mass spectrum for each analyzed pixel. The third newly developed detection mode available within the instrument is a position sensitive transmission detector located at the backside of the sample in order to detect the transmitted He beam. This scanning transmission helium ion microscopy (STHIM) mode provides further in-situ structural/compositional data with tomographic capabilities.
In order to optimize the analysis of biological samples, one further key feature of the instrument is a 5-axis cryo-stage along with cryo-capabilities for sample transfers. This cryo-capability allows biological samples to be analyzed in a frozen-hydrated state, thus avoiding artefacts caused by classical sample preparation (e.g. chemical fixation) used for HV or UHV imaging of biological specimens at room temperature. Moreover, the cryo-mode can be beneficial for analyzing beam sensitive samples in materials science such as OLEDs and polymers.
In this work we will present the npSCOPE concept and the instrument’s overall setup, report on the performance of the different detection modes and discuss the correlative microscopy capabilities. We will present results from case studies in different fields, with a particular focus on nanoparticles (see Figure 1) [9].

Keywords: Helium Ion Microscopy; Scanning transmission ion microscopy; SIMS

  • Lecture (Conference)
    Microscopy & Microanalysis 2020, 02.-06.08.2020, Milwaukee, USA

Permalink: https://www.hzdr.de/publications/Publ-30808
Publ.-Id: 30808


Why should we care about microorganisms in the bentonite back fill material for the storage of high-level radioactive waste in deep geological repositories?

Matschiavelli, N.; Dressler, M.; Neubert, T.; Kluge, S.; Schierz, A.; Cherkouk, A.

Every year 12,000 metric tonnes of high-level radioactive waste (HLW) are produced worldwide. For the long-term storage of this highly radiotoxic waste, a deep geological disposal by using multiple barriers is favored. Bentonite is proposed as a potential material for sealing the space between the canister containing the HLW and the surrounding host rock. In order to investigate the microbial diversity and metabolic activity of naturally occurring microorganisms as well as their time-dependent evolution, we conducted anaerobic microcosm experiments containing bentonite and a synthetic Opalinus Clay pore water solution. During the one-year incubation at 30 and 60 °C, lactate- or H2-stimulated microcosms at 30 °C showed the dominance and activity of strictly anaerobic, sulfate-reducing and spore-forming microorganisms. The subsequent generation of hydrogen sulfide gas in the respective set ups, led to the formation of fractures and iron-sulfur precipitations. In microcosms that incubated at 60 °C, thermophilic bacteria dominated, independent from the availability of substrates. In the respective microcosms, no significant metabolic activity was detected and there was no change in the analyzed bio-geochemical parameters. Our results show that indigenous microorganisms evolve in a temperature- and substrate-dependent manner. Potentially formed metabolites could affect the dissolution behavior of minerals and ions within the bentonite as well as the corrosion process of the canister material and require further investigations.

  • Lecture (Conference)
    6th Joint Conference of DGHM & VAAM, 08.-11.03.2020, Leipzig, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30807
Publ.-Id: 30807


The Potential Role of Colloidal Silica as a Depressant in Scheelite Flotation

Kupka, N.; Babel, B. M.; Rudolph, M.

The main challenge in scheelite flotation lies in the contamination of the concentrate by other calcium-bearing minerals, mainly calcite. To remedy this problem, sodium silicate is frequently used as a depressant. According to the literature, one hypothesis for the mechanism of water glass consists in its absorption onto calcite through colloidal silica formation, preventing hydrophobization by the collector. This short communication presents research conducted on the direct use of colloidal silica as a depressant in scheelite flotation. Colloidal silica is shown to have an impact on scheelite flotation, especially by depressing silicates.

Keywords: scheelite flotation; colloidal silica; depressant

Permalink: https://www.hzdr.de/publications/Publ-30806
Publ.-Id: 30806


Acidified water glass in the selective flotation of scheelite from calcite, Part I: performance and impact of the acid type

Kupka, N.; Möckel, R.; Rudolph, M.

To improve the performance of sodium silicate in scheelite flotation and allow the selective separation of scheelite from other semi-soluble salt-type minerals such as calcite, three acids, sulfuric, oxalic and for the first time hydrochloric are used to acidify sodium silicate (also called water glass). A literature review of previous usage of acidified water glass shows that no comparison between acids was made before, that comparisons with alkaline water glass were limited and that the idea that acidified water glass is more efficient at lower dosages has not been proven in scheelite flotation. As a consequence, the impact of the acid type, the ratio between acid and sodium silicate and acid dosage is tested in single mineral flotation and batch flotation experiments. All three acids allow a higher performance of acidified water glass compared to alkaline water glass at lower dosages and with little addition of acid: the tungsten recovery and grade are improved while silicates and to a lesser extent calcium-bearing minerals float less. The dosage of acid is less determining than the mass ratio of the acid to sodium silicate, except in the case of hydrochloric acid. Overall, the acid type does not matter as all three acids perform well in flotation, whereby oxalic and hydrochloric acid are better.

Keywords: acidified water glass; scheelite calcite separation; froth flotation

  • Open Access Logo Physicochemical Problems of Mineral Processing 56(2020)2, 238-251
    DOI: 10.37190/ppmp19101

Permalink: https://www.hzdr.de/publications/Publ-30805
Publ.-Id: 30805


Rapid Thermodynamically Stable Complex Formation of [nat/111In]In3+, [nat/90Y]Y3+, and [nat/177Lu]Lu3+ with H6dappa

Kostelnik, T.; Xiaozhu, W.; Southcott, L. D.; Wagner, H.; Kubeil, M.; Stephan, H.; Jaraquemada-Pelaez, M. D. G.; Orvig, C.

A phosphinate-bearing picolinic acid-based chelating ligand (H6dappa) was synthesized and characterized to assess its potential in a bifunctional chelator (BFC) for inorganic radiopharmaceuticals. Nuclear magnetic resonance (NMR) spectroscopy was employed to investigate the chelator coordination chemistry with a variety of nonradioactive trivalent metal ions (In3+, Lu3+, Y3+, Sc3+, La3+, Bi3+). Density functional theory (DFT) calculations explored the coordination environments of aforementioned metal complexes. The thermodynamic stability of H6dappa with four metal ions (In3+, Lu3+, Y3+, Sc3+) was deeply investigated via potentiometric and spectrophotometric (UV-vis) titrations, employing a combination of acidic in-batch, joint potentiometric/spectrophotometric, and ligand-ligand competition titrations; high stability constants and pM values were calculated for all four metal complexes. Radiolabeling conditions for three clinically relevant radiometal ions were optimized ([111In]In3+, [177Lu]Lu3+, [90Y]Y3+), and the serum stability of [111In][In(dappa)]3- was studied. Through concentration-, time-, temperature-, and pH-dependent labeling experiments, it was determined that H6dappa radiolabels most effectively at near-physiological pH for all radiometal ions. Furthermore, very rapid radiolabeling at ambient temperature was observed, as maximal radiolabeling was achieved in less than one minute. Molar activities of 29.8 GBq/mol and 28.2 GBq/mol were achieved for [111In]In3+ and [177Lu]Lu3+, respectively.

Permalink: https://www.hzdr.de/publications/Publ-30804
Publ.-Id: 30804


Special issue of the American Journal of Science

Fischer, C.; Arvidson, R. S.

This is the second part of a special issue of the American Journal of Science examining a problem that defines, perhaps more than any other, the state-of-the-art in the geochemistry of fluid-solid interaction: how to integrate data from both observations and modeling of events of brief duration at essentially atomic scales (for example, attachment, diffusion, detachment, hydrolysis), to that of mesoscale, ensemble processes (crystal dissolution, growth, alteration). The ultimate goal is an understanding of the long-term, phenomenological consequences of these interactions, often termed “upscaling”. Success in predicting and constraining these latter outcomes determines the larger value of this field, both to neighbors in environmental sciences and engineering, as well as to the public in terms of policy, education, and support. Nanoscale observation of mineral surfaces via instruments such as AFM and VSI is now widespread; increases in resolution and analytical capability of these instruments have also evolved in tandem with advances in the power and resolution of simulation and modeling approaches. Closely tied to an emerging theoretical framework, this “soft” progress in simulation and modeling was the focus of the first part of this issue.

  • Book (Editorship)
    New Haven CT 06220-8109: American Journal of Science, Yale University, 2020
    101 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-30803
Publ.-Id: 30803


Resource Efficiency Evaluation of Pyrometallurgical Solutions to Minimize Iron-Rich Residues in the Roast-Leach-Electrowinning Process

Abadias Llamas, A.; Bartie, N.; Heibeck, M.; Stelter, M.; Reuter, M. A.

The Roast-Leach-Electrowinning process generates considerable quantities of iron-rich precipitates that must be landfilled, potentially causing a problem for the zinc smelters as well as negatively affecting the society and the environment. The integration of pyrometallurgical flowsheets into existing Roast-Leach-Electrowinning plants is evaluated in this paper. Ten different cases, including Direct Zinc Smelting, ferrite fuming or pyrometallurgical treatment of iron-rich residue, are assessed to find the most resource efficient and environmentally friendly solution to minimize the hydrometallurgical precipitates of the electrolytic process for the zinc production. The simulation-based methodology used provides indicators to evaluate the material recovery and losses, residue production, resource consumption, exergy destruction, and environmental impacts, which are used to find the best alternative that improves the resource efficiency and the environmental impact of the Roast-Leach-Electrowinning process. Furthermore, the social, environmental, and economic impacts associated to the different alternatives are discussed based on the indicators provided by the simulation.

Keywords: Exergy; Thermoeconomics; Process simulation; Sustainability evaluation; Jarosite treatment

  • Contribution to proceedings
    PbZn 2020: 9th International Symposium on Lead and Zinc Processing, 23.-27.02.2020, San Diego, United States
    PbZn 2020: 9th International Symposium on Lead and Zinc Processing: Springer, Cham, 978-3-030-37069-5, 351-364
    DOI: 10.1007/978-3-030-37070-1_31

Permalink: https://www.hzdr.de/publications/Publ-30802
Publ.-Id: 30802


Late complications following neo-/adjuvant radiotherapy and surgery for sarcomas of the extremities or pelvis/retroperitoneum Preventative measures

Jentsch, C.; Hofbauer, C.; Makocki, S.; Troost, E. G. C.

Radiotherapy is one of the pillars in the multimodal therapy of sarcomas of the extremities or pelvis/retroperitoneum. It can be delivered prior to or following surgery. Novel radiation techniques, such as intensity-modulated radiotherapy using high-energy photons or protons, contribute to the reduction of acute and late toxicities. This review article summarizes these concepts.

Keywords: Limb; Photon beam therapy; Proton beamtherapy; Radiotherapy, intensity-modulated; Soft tissue neoplasms

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  • Secondary publication expected from 12.02.2021

Permalink: https://www.hzdr.de/publications/Publ-30801
Publ.-Id: 30801


L1 cell adhesion molecule confers radioresistance to ovarian cancer and defines a new cancer stem cell population

Terraneo, N.; Jacob, F.; Peitzsch, C.; Dubrovska, A.; Krudewig, C.; Huang, Y.-L.; Heinzelmann-Schwarz, V.; Schibli, R.; Béhé, M.; Grünberg, J.

Many solid tumors, including ovarian cancer, contain small populations of cancer stem cells (CSCs). These cells are usually resistant against conventional cancer therapies and play a role in disease recurrence. We demonstrated that the L1 cell adhesion molecule (L1CAM) is a new CSC target in ovarian cancer, triggering radioresistance. Using fluorescence-activated cell sorting, specific cell populations expressing L1CAM alone or in combination with the established CSC marker CD133 were isolated from three ovarian cancer cell lines. Double-positive L1CAM+/CD133+ cells displayed higher spherogenic and clonogenic properties in comparison to L1CAM−/CD133− cells. Furthermore, L1CAM+/CD133+ cells retained highest clonogenic capacity after irradiation and exhibited up-regulation of some CSC-specific genes, enhanced tumor-initiating capacity, selfrenewal and higher tumor take rate in nude mice when compared with other cell populations. Superior radioresistance by L1CAM expression was confirmed by deletion of L1CAM using CRISPR-Cas9 technology. Moreover, we found expression signatures associated with epithelial-tomesenchymal transition phenotype in L1CAM deleted cells. These results indicate that L1CAM in combination with CD133 defines a new cancer cell population of ovarian tumor-initiating cells with the implication of targeting L1CAM as a novel therapeutic approach for ovarian CSCs.

Keywords: L1 cell adhesion molecule; ovarian cancer; stem cells; radioresistance; CRISPR-Cas9; epithelial-to-mesenchymal transition

Permalink: https://www.hzdr.de/publications/Publ-30800
Publ.-Id: 30800


Identification of the regime boundaries in bubble columns based on the degree of randomness in the signals

Nedeltchev, S.; Top, Y.; Hlawitschka, M. W.; Schubert, M.; Bart, H.-J.

A new parameter (degree of randomness (DR)) was defined for the identification of the main transition velocities, Utrans. The new method reconstructs the time series into multiple state vectors, thus generating non-overlapping vector pairs and then compares the distance between them with a pre-selected cut-off length. The DR values were extracted from gauge and differential pressure fluctuations as well as x-ray tomographic scans. At every Utrans value, the DR index exhibited a well-pronounced local minimum. Three cylindrical bubble columns (BCs) with various diameters (0.1, 0.14, and 0.45 m in ID) and one rectangular BC (width = 0.2 m, depth = 0.04 m) were used. They were aerated by means of different perforated plate gas distributors. It was found that in the cylindrical BCs the disintegration of the bubbly flow regime took place always at Utrans = 0.04 m/s. In the case of the rectangular BC the first critical velocity appeared at Utrans = 0.012 m/s. The lower boundary of the churn-turbulent regime was identified at Utrans = 0.11 m/s in the smallest cylindrical BC and at about Utrans = 0.095 m/s in the other two cylindrical BCs. In the case of the rectangular BC, the second critical velocity was identified at Utrans = 0.039 m/s. The low Utrans in the rectangular BC imply that the hydrodynamic regimes are less stable in this particular column due to higher degree of liquid turbulence. The calculated DR values from the gauge pressure fluctuations successfully distinguished the upper boundary of the gas maldistribution and the first transition sub-regime.

Keywords: bubble columns; pressure fluctuations; regime transitions; signal randomness; tomographic scans

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Permalink: https://www.hzdr.de/publications/Publ-30799
Publ.-Id: 30799


Random singlet state in Ba5CuIr3O12 single crystals

Volkov, P. A.; Won, C.-J.; Gorbunov, D.; Kim, J.; Ye, M.; Kim, H.-S.; Pixley, J. H.; Cheong, S.-W.; Blumberg, G.

We study the thermodynamic and high-magnetic-field properties of the magnetic insulator Ba5CuIr3O12, which shows no magnetic order down to 2 K, consistent with a spin-liquid ground state. While the temperature dependence of the magnetic susceptibility and the specific heat shows only weak antiferromagnetic correlations, we find that the magnetization does not saturate up to a field of 59 T, leading to an apparent contradiction. We demonstrate that the paradox can be resolved, and all of the experimental data can be consistently described within the framework of random singlet states. We demonstrate a generic procedure to derive the exchange coupling distribution P(J ) from the magnetization measurements and use it to show that the experimental data are consistent with the power-law form P(J ) ∼ J−α with α ≈ 0.6. Thus, we reveal that high-magnetic-field measurements can be essential to discern quantum spin-liquid candidates from disorder dominated states that do not exhibit long-range order.

Permalink: https://www.hzdr.de/publications/Publ-30798
Publ.-Id: 30798


Spin-lattice coupling in a ferrimagnetic spinel: Exotic H-T phase diagram of MnCr2S4 up to 110 T

Miyata, A.; Suwa, H.; Nomura, T.; Prodan, L.; Felea, V.; Scurschii, I.; Deisenhofer, J.; Krug Von Nidda, H.-A.; Portugall, O.; Zherlitsyn, S.; Tsurkan, V.; Wosnitza, J.; Loidl, A.

In antiferromagnets, the interplay of spin frustration and spin-lattice coupling has been extensively studied as the source of complex spin patterns and exotic magnetism. Here, we demonstrate that, although neglected in the past, the spin-lattice coupling is essential to ferrimagnetic spinels as well. We performed ultrahigh-field magnetization measurements up to 110 T on a Yafet-Kittel ferrimagnetic spinel, MnCr2S4, which was complemented by measurements of magnetostriction and sound velocities up to 60 T. Classical Monte Carlo calculations were performed to identify the complex high-field spin structures. Our minimal model incorporating spin-lattice coupling accounts for the experimental results and corroborates the complete phase diagram, including two new high-field phase transitions at 75 and 85 T.Magnetoelastic coupling induces striking effects: An extremely robust magnetization plateau is embedded between two unconventional spin-asymmetric phases. Ferrimagnetic spinels provide a new platform to study asymmetric and multiferroic phases stabilized by spin-lattice coupling.

Permalink: https://www.hzdr.de/publications/Publ-30796
Publ.-Id: 30796


High-field phase transitions in the orbitally ordered multiferroic GeV4S8

Felea, V.; Pham, T. C.; Prodan, L.; Gorbunov, D.; Nomura, T.; Scurschii, I.; Zherlitsyn, S.; Wosnitza, J.; Wang, Z.; Miyata, A.; Portugall, O.; Widmann, S.; Krug Von Niddy, H.-A.; Deisenhofer, J.; Tsurkan, V.; Loidl, A.

The high-field (H,T) phase diagram of the multiferroic lacunar spinel GeV4S8 has been studied by ultrasound, magnetization, and pyrocurrent experiments in magnetic fields up to 60 T. The title compound consists of molecular building blocks, with vanadium V4 clusters characterized by a unique electron density. These vanadium tetrahedra constitute a Jahn-Teller active entity, which drive an orbital-ordering transition at 30K with the concomitant appearance of ferroelectricity. Ultrasound and magnetization experiments reveal sharp anomalies in magnetic fields of 46 T, which are associated with a first-order phase transition into an orbitally disordered state characterized by significant field and temperature hystereses. We report a sequence of complex magnetic, polar, and orbitally ordered states, i.e., the appearance of two orbitally ordered phases OO1 and OO2 for μ0H < 45 T and T < 30K. Beyond the paraelectric phase we further evidenced three ferroelectric phases, FE1, FE2, and FE3. Finally, antiferromagnetic (AFM) order (T < 15 K) and fully polarized ferromagnetic order (μ0H > 60 T) have been observed in GeV4S8. At low temperatures and for fields below 40 T, AFM order coexists with the polar phase FE3 identifying a multiferroic state. Our results demonstrate a fascinating competition of the different orders, which the material manifests in high magnetic fields and at low temperatures.

Permalink: https://www.hzdr.de/publications/Publ-30795
Publ.-Id: 30795


Structure and magnetic properties of (Sm,Ho)2Fe17Nx (x = 0; 2.4)

Veselova, S. V.; Tereshina, I. S.; Verbetsky, V. N.; Neznakhin, D. S.; Tereshina-Chitrova, E. A.; Kaminskaya, T. P.; Karpenkov, A. Y.; Akimova, O. V.; Gorbunov, D.; Savchenko, A. G.

The structural and magnetic properties of the compound Sm1.2Ho0.8Fe17 and the nitride powders Sm1.2Ho0.8Fe17N2.4 prepared by high energy ball milling under various milling regimes are reported. Magnetic properties of the samples are investigated at 2–300 K in steady magnetic field up to 70 kOe and in pulsed magnetic field up to 600 kOe. The application of high magnetic field reveals the presence of the second-order transition in Sm1.2Ho0.8Fe17N2.4 at 500 kOe. Magnetic hysteresis properties study shows that ball milling enhances magnetic performance of Sm1.2Ho0.8Fe17N2.4 making it perspective for the magnets fabrication.

Permalink: https://www.hzdr.de/publications/Publ-30794
Publ.-Id: 30794


Noncollinear magnetic structure in U2Pd2In at high magnetic fields

Prokes, K.; Bartkowiak, M.; Gorbunov, D.; Prokhnenko, O.; Rivin, O.; Smeidbidl, P.

We report an unexpected magnetic-field-driven magnetic structure in the 5 f -electron Shastry-Sutherland system U2Pd2In. This phase develops at low temperatures from a noncollinear antiferromagnetic ground state above the critical field of 25.8 T applied along the a axis. All U moments have a net magnetic Moment in the direction of the applied field, described by a ferromagnetic propagation vector qF = (0 0 0) and an antiferromagnetic component described by a propagation vector qAF = (0 0.30 1/2 ) due to a modulation in the direction perpendicular to the applied field. We conclude that this surprising noncollinear magnetic structure is due to a competition between the single-ion anisotropy trying to keep moments, similar to the ground state, along the [110]-type directions, Dzyaloshinskii-Moryia interaction forcing them to be perpendicular to each other and application of the external magnetic field attempting to align them along the field direction.

Permalink: https://www.hzdr.de/publications/Publ-30793
Publ.-Id: 30793


Slurm in Docker

Pape, D.

A Docker image with a Slurm setup to enable testing of HPC software in a container.

Keywords: Docker; Slurm; batch system; high performance computing; research software development

  • Software in external data repository
    Publication year 2020
    Programming language: Dockerfile, Shell
    System requirements: Docker Engine
    License: GPL v3 (Link to license text)
    Hosted on https://gitlab.hzdr.de/fwcc/slurm-in-docker:

Permalink: https://www.hzdr.de/publications/Publ-30792
Publ.-Id: 30792


GitLab HPC Driver Protoype

Pape, D.

GitLab HPC Driver prototype implementation.

Keywords: continuous integration; high performance computing; GitLab; Slurm; batch system; scientific software; research software development

  • Software in external data repository
    Publication year 2020
    Programming language: Bash
    System requirements: Linux
    License: GPL v3 (Link to license text)
    Hosted on https://gitlab.hzdr.de/fwcc/gitlab-hpc-driver-prototype:

Permalink: https://www.hzdr.de/publications/Publ-30791
Publ.-Id: 30791


GitLab HPC Driver

Pape, D.

Um gute Performance und Skalierbarkeit von hochparalleler wissenschaftlicher Software sicherzustellen, ist es wichtig, diese in einer möglichst realitätsnahen Umgebung zu testen. Wünschenswert ist dabei ein möglichst einfacher Zugriff auf die HPC-Ressourcen über ein bereits etabliertes System wie GitLab CI. Dafür wurde ein Driver für den GitLab-Runner entwickelt, der es erlaubt Continuous-Integration-Jobs auf Hochleistungsrechnern auszuführen. Der Driver wird vom GitLab-Runner-Service aufgerufen und kann vom Nutzer auf die gleiche Art und Weise verwendet werden, wie andere im GitLab-Ökosystem bekannte CI-Systeme. Es werden HPC-Ressourcen unterstützt, die vom Batchsystem Slurm verwaltet werden.

To ensure high performance and scalability in scientific software, a realistic testing environment plays an important role. Preferably, easy access to HPC resources is enabled via an established tool like GitLab CI. For that, a driver for GitLab runner has been developed that allows the execution of CI jobs on a supercomputer. The driver is called by GitLab runner service and can be used in the same way as other tools in the GitLab ecosystem. It supports HPC resources managed by the Slurm batch system.

Keywords: continuous integration; high performance computing; GitLab; Slurm; batch system; scientific software; research software development

  • Software in external data repository
    Publication year 2020
    Programming language: C++
    System requirements: Linux
    License: GPL v3 (Link to license text)
    Hosted on https://gitlab.hzdr.de/fwcc/gitlab-hpc-driver:

Permalink: https://www.hzdr.de/publications/Publ-30790
Publ.-Id: 30790


Two-Pion Intensity Interferometry in Au + Au @ 1.23A GeV

Greifenhagen, R.; (for the HADES collaboration)

High-statistics π−π− HBT data for non-central Au + Au collisions at 1.23A GeV, measured with HADES at SIS18/GSI, are presented. The three-dimensional emission source is studied in dependence on pair transverse momentum and centrality. A tilt of the source relative to the beam axis is observed. The spatial extension and the tilt magnitude of the source decrease with transverse momentum. The spatial extension decreases and the tilt magnitude increases going from central to peripheral collisions. The derived eccentricity perpendicular to the beam axis fits well to the initial nucleonic overlap region at high transverse momentum.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-30789
Publ.-Id: 30789


The tectono-sedimentary evolution of a major seismogenic zone with low slip rate activity: A geochronological and sedimentological investigation of the Dobrá Voda Depression (Western Carpathians)

Šujan, M.; Braucher, R.; Šujan, M.; Hók, J.; Povinec, P. P.; Šipka, F.; Rugel, Georg; Scharf, A.

Seismically active fault zones receive a great deal of attention due to their potential for quantification of seismic hazards. Zones with low slip rates pose a challenge, however, since their poor topographic expression is related to difficulties in the quantification of fault movement. This study focuses on the Dobrá Voda Depression, an area with the highest level of seismic activity in the Western Carpathians. The Quaternary tectono-sedimentary evolution of the small intramontane basin was investigated with the use of facies analysis of cores, dated with the use of cosmogenic nuclide depth profiles (10Be, 26Al and 36Cl), together with 26Al/10Be burial dating and radiocarbon dating. A set of archived boreholes and geoelectric survey data was used for the correlation of results with those from new boreholes across the depression. Four facies associations were distinguished: (FA1) Colluvial deposits that comprise subaerial debris flows and mudflows; (FA2) Fluvial deposits with high sediment supply: accommodation ratio, composed mostly of sandy-gravelly channel fill facies; (FA3) Fluvial deposits with low sediment supply: accommodation ratio, consisting mostly of floodplain muds, overbank heterolithic facies and minor sandy-gravelly channel fills; and (FA4) Swamp deposits, which are mostly made up of peat. Geochronological results suggest that the studied part of FA3 was deposited before 1.0 Ma due to a rise in the base level following a major incision event. Overbank-dominated deposits of FA3 covered an incision surface, resulted in a difference of ca. 65 m of elevation of these strata, which represents the minimal thickness of FA3. The second phase of incision was related to reactivation of Miocene normal faults resulting in further topographic differentiation. The initiation of fault activity is recorded by the deposition of colluvial FA1 before ca. 250 ka. FA2 accumulated between ca. 160 and 100 ka, mostly at the toes of slopes bounding the fault scarps on the basin margins. The last documented phase of evolution represents an increase of accommodation, which was connected to the deposition of Holocene peat in swamps as well as floodplain muds of FA4 above FA2. The observed settings imply that variation between incision and accumulation in a scale of hundreds of thousands of years is characteristic for low relief tectonically active zones. The presented research demonstrates the significance of sedimentological analysis for reconstruction of tectonic evolution in areas with low slip rate activity.

Keywords: Depth profile exposure dating of 10Be; 26Al and 36Cl; AMS

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  • Secondary publication expected from 12.02.2021

Permalink: https://www.hzdr.de/publications/Publ-30788
Publ.-Id: 30788


Positron annihilation analysis of nanopores and growth mechanism of oblique angle evaporated TiO₂ and SiO₂ thin films and multilayers

García-Valenzuela, A.; Butterling, M.; Liedke, M. O.; Hirschmann, E.; Trinh, T. T.; Elsherif, A. G. A.; Wagner, A.; Alvarez, R.; Gil-Rostra, J.; Rico, V.; Palmero, A.; González-Elipe, A. R.

The nano-porosity embedded into the tilted and separated nanocolumns characteristic of the microstructure of evaporated thin films at oblique angles has been critically assessed by various variants of the positron annihilation spectroscopy. This technique represents a powerful tool for the analysis of porosity, defects and internal interfaces of materials, and has been applied to different as-deposited SiO₂ and TiO₂ thin films as well as SiO₂/TiO₂ multilayers prepared by electron beam evaporation at 70° and 85° zenithal angles. It is shown that, under same deposition conditions, the concentration of internal nano-pores in SiO₂ is higher than in TiO₂ nanocolumns, while the situation is closer to this latter in TiO₂/SiO₂ multilayers. These features have been compared with the predictions of a Monte Carlo simulation of the film growth and explained by considering the influence of the chemical composition on the growth mechanism and, ultimately, on the structure of the films.

Keywords: Positron annihilation; Nanopores; OAD thin films; TiO₂; SiO₂; Growing mechanism

Permalink: https://www.hzdr.de/publications/Publ-30787
Publ.-Id: 30787


Revealing the defect-dominated oxygen evolution activity of hematene

Bishnupad, M.; Wei, Y.; Ghorbani Asl, M.; Krasheninnikov, A.; Parasmani, R.; Bikash, K. J.

Oxygen electrocatalysis is vital for advanced energy technologies, but inordinate challenges remain due to the lack of highly active earth-abundant catalysts. Herein, by nanostructuring and defect engineering, we enhance the catalytic properties of naturally occurring, but normally inactive ore hematite (Ht) by converting it to hematene (Hm) with oxygen vacancies (Ov-Hm), that becomes an efficient oxygen evolution reaction (OER) catalyst, being even superior to the state-of-the-art catalyst IrO2/C, with a current density of 10 mA/cm2 at a lower overpotential of 250 mV. The first-principles calculations reveal that the reduced dimensionality and defects on the Hm surface locally modify the charge around the adsorption sites, which results in a reduction of the potential barrier in the OER process. Our experimental and theoretical insights suggest a promising route to the development of a highly active electrocatalyst from the naturally occurring and abundant material for OER applications.

Keywords: hemetene; defect; electrocatalysis; oxygen evolution reaction

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  • Secondary publication expected from 03.03.2021

Permalink: https://www.hzdr.de/publications/Publ-30786
Publ.-Id: 30786


Chelation in One Fell Swoop: Optimizing Ligands for Smaller Radiometal Ions

Choudhary, N.; Jaraquemada-Pelaez, M.; Zarschler, K.; Wang, X.; Radchenko, V.; Kubeil, M.; Stephan, H.; Orvig, C.

44/47Sc3+, 68Ga3+ and 111In3+ are the three most attractive trivalent smaller radiometalnuclides, offering a wide range of distinct properties (emission energies and types) in the toolbox of nuclear medicine. In this study, all three of the metal ions are successfully chelated using a new oxine-based hexadentate ligand, H3glyox, which forms thermodynamically stable and kinetically inert neutral complexes with exceptionally high pM values [pIn (34) > pSc (26) > pGa (24.9)]. X-ray diffraction single crystal structures with stable isotopes revealed that the ligand is highly preorganized and has a perfect fit to size cavity to form [Sc(glyox)(H2O)] and [In(glyox)(H2O)] complexes. Quantitative radiolabeling of 68Ga (RCY > 95%, [L]= 10-5 M) and 111In (RCY > 99%, [L]= 10-8 M) was achieved at ambient conditions (RT, pH 7 and 15 min) with very high apparent molar activities of 750 MBq/mol and 650 MBq/nmol, respectively. Preliminary quantitative radiolabeling of 44ScCl3 (RCY > 99%, [L] = 10-6 M) was fast at room temperature (pH 7 and 10 min). In vitro experiments revealed exceptional stability of both 68Ga(glyox) and 111In(glyox) complexes against human serum (rate of transchelation < 2%) and its suitability for biological applications. Additionally, on chelation with metal ions, H3glyox exhibits enhanced fluorescence which was employed to determine the stability constants for Sc(glyox) complex in addition to the in-batch UV-vis spectrophotometric titrations; as a proof-of-concept these complexes were used to obtain fluorescence images of live HeLa cells using natSc(glyox) and natGa(glyox), confirming the viability of the cells. These initial investigations suggest H3glyox to be a valuable chelator for radiometalbased diagnosis (nuclear and optical imaging) and therapy.

Permalink: https://www.hzdr.de/publications/Publ-30785
Publ.-Id: 30785


Numerical simulation of formation and growth of fractal-like aggregates in a tubular aerosol reactor

Lehnigk, R.; Niemi, T.; Peltola, J.; Schlegel, F.

Ceramic powders produced by gas phase synthesis frequently consist of non-spherical, fractal-like particle aggregates. Their shape is a result of the simultaneous action of particle coagulation and sintering. Coagulation describes the process of particle agglomeration, e.g. due to ballistic or diffusion-limited collisions, whereas sintering stands for coalescence of primary particles and acts to create denser aggregates. A low density aggregate has a larger collisional cross-section and thus is more likely to collide with other particles or aggregates, which is reflected in the development of the aggregate size distribution and should be taken into account when modeling the process. To this end, a class method based population balance modeling approach available in OpenFOAM was extended to allow for a simplified bivariate treatment. Among the many shape-characterizing parameters, the average surface-area-to-volume ratio of each size class is tracked by a separate transport equation. Together with a fixed fractal dimension, it can be translated into a collisional diameter and further used when calculating coagulation rates. The functionality is showcased by a simulation of the vapor synthesis of Titania in a tubular aerosol reactor [Akhtar et al., AlChE J., 37(10): 1561-1570, 1991]. Data from a differential mobility sizer is used to validate the approach.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Computational Fluid Dynamics und Gasreinigung, 09.-11.03.2020, Bamberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30784
Publ.-Id: 30784


Spin-polarized positrons. Who cares?

Wagner, A.; Butterling, M.; Liedke, M. O.; Hirschmann, E.; Elsherif, A. G. A.

Proposal for a spin-polarized positron beam facility at the upcoming DALI facility

Keywords: spin-polarized positrons

  • Lecture (others)
    Treffen deutschsprachiger Positronengruppen, 13.-14.02.2020, Halle (Saale), Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30783
Publ.-Id: 30783


Materials Research with Positrons – From atomic defects to nano-scale porosimetry

Wagner, A.

Materials Research with Positrons – From atomic defects to nano-scale porosimetry

Keywords: Materials Research Positrons atomic defects nano-scale porosimetry

  • Invited lecture (Conferences)
    Spectroscopic methods and synchrotron XRD for materials characterization, 05.03.2020, Kista, Sweden

Permalink: https://www.hzdr.de/publications/Publ-30782
Publ.-Id: 30782


Elucidating the mechanism of uranium uptake and processing in tobacco BY-2 cells

John, W.; Matschiavelli, N.; Thieme, D.; Hoehenwarter, W.; Sachs, S.

The release of uranium from waste repositories into the ground water and surrounding soil can have adverse effects on the biomes of affected sites. The bioavailability and chemical toxicity of U(VI) species, which are the most prevalent in oxic environments of soils and water bodies, can pose serious threats as they are transferred through the food chain. Despite remediation strategies employing the cultivation of crop plants to sequester uranium, little is known of the mechanisms used by plants in processing the uranium species that they encounter. The aim of this research therefore has been to shed light on the pathways involved in the uptake and processing of uranium by plant cells, using the undifferentiated tobacco BY-2 cells as model plant cells. Former experiments showing increases in the cytoplasmic glutathione pools upon exposure of Brassica napus cell cultures to uranium have led us to the hypothesis that tobacco cells are able to reduce U(VI) to U(IV). This research describes a novel method of exposing BY-2 cells to U(VI) in phosphate deficient medium, which maintains relatively high cell viability under phosphate deficient conditions, and reveals differentially expressed proteins in the presence of uranium. Uranium-spiked culture medium was seen to affect the uptake of trace elements and minerals as well as show changes in the profiles of polyacrylamide-resolved proteins. Proteomics is being used to identify candidate proteins involved in the processing of uranium by the cells and microscopic visualization techniques are utilized to confirm these pathways and mechanisms.

Acknowledgments: This work is funded by the German Federal Ministry of Education and Research under the contract number 02NUK051B.

Keywords: uranium; nuclear waste; metal uptake; tobacco cells

  • Lecture (Conference) (Online presentation)
    Biometals 2020, 05.-09.07.2020, Villard de Lans, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-30779
Publ.-Id: 30779


P1817 - Sensor zur Vermessung von Strömungsprofilen in großen Kolonnen und Apparaten

Vishwakarma, V.; Schleicher, E.; Schubert, M.; Tschofen, M.; Löschau, M.

Gegenstand der vorliegenden Erfindung ist eine Vorrichtung zur Bestimmung des Strömungsprofils von Mehrphasenströmungen mit mindestens einer Flüssigkeitskomponente mit vorgegebener Strömungsrichtung. Die Vorrichtung weist eine Mehrzahl von stabförmigen Sonden auf. Jede der Sonden weist zwei parallel verlaufende Elektroden aus, die in einer gemeinsamen elektrisch isolierenden Umhüllung angeordnet sind. Darüber hinaus weist jede Sonde mindestens eine Abschirmelektrode auf. Eine Elektrode jeder Sonde fungiert als Transmitter (Sender) und die zweite Elektrode jeder Sonde als Receiver (Empfänger). Eine Auswerteeinheit ist dazu eingerichtet, die Transmitterelektrode jeder Sonde mit elektrischer Spannung als Messspannung zu beaufschlagen und das Ergebnissignal an der Receiverelektrode derselben Sonde zu erfassen. Mindestens zwei Sonden sind zu einer Gruppe zusammengefasst, wobei die Auswerteeinheit zum gleichzeitigen Beaufschlagen der Sonden dieser Gruppe mit der Messspannung ausgebildet ist.

  • Patent
    DE102018124501 - Erteilung 13.02.2020

Permalink: https://www.hzdr.de/publications/Publ-30778
Publ.-Id: 30778


Essential Role of Heterocyclic Structure of N-Alkylated 2-Pyrrolidone Derivatives for Recycling Uranium from Spent Nuclear Fuels

Inoue, T.; Kazama, H.; Tsushima, S.; Takao, K.

In a simple and versatile reprocessing method for recycling U and Pu from spent nuclear fuels, cyclic amides like N-alkylated 2-pyrrolidone derivatives (NRPs) are exclusively employed. However, there have been no convincing rationales why such a heterocyclic structure is required. To answer this question, we employed N-cyclohexyl-2-pyrrolidone (NCP) and N-cyclohexylformamide (NCF) as cyclic and acyclic monodentate amides, and focused on the following 3 topics in this study; (1) structural chemistry of their uranyl dinitrato complexes, (2) precipitation behavior of UO22+ from HNO3(aq) by using these amides, and (3) their chemical stability in HNO3(aq) simulating the reprocessing process for spent nuclear fuels. Fundamental coordination chemistry of UO2(NO3)2(L)2 (L = NCP, NCF) were found to be common to both L, regardless of the presence or absence of the pyrrolidone ring. Furthermore, both L exhibit comparable capability in precipitation of UO22+ from HNO3(aq). The most critical difference between NCP and NCF was found in their chemical stability in HNO3(aq), where NCF was gradually decomposed through acid-catalyzed hydrolysis, while NCP remained intact for at least 4 h. In conclusion, the pyrrolidone ring of NRPs plays an important role to protect the carbonyl C from nucleophilic hydrolysis which initiates the amide C(=O)−N bond cleavage.

Permalink: https://www.hzdr.de/publications/Publ-30776
Publ.-Id: 30776


Annual Report 2019 - Institute of Resource Ecology

Stumpf, T.; Foerstendorf, H.; Bok, F.; Richter, A.

The Institute of Resource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden –Rossendorf (HZDR). Our research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Ra-diation Research (NUSAFE)” of the Helmholtz Association (HGF) and focused on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”. The program NUSAFE, and therefore all work which is done at IRE, belong to the research field “Energy” of the HGF...

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-110 2020
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-30774
Publ.-Id: 30774


Magnetic response of FeRh to static and dynamic disorder

Eggert, B.; Schmeink, A.; Lill, J.; Liedke, M. O.; Kentsch, U.; Butterling, M.; Wagner, A.; Pascarelli, S.; Potzger, K.; Lindner, J.; Thomson, T.; Fassbender, J.; Ollefs, K.; Keune, W.; Bali, R.; Wende, H.

Atomic scale defects generated using focused ion as well as laser beams can activate ferromagnetism in initially non-ferromagnetic B2 ordered alloy thin film templates. Such defects can be induced locally, confining the ferromagnetic objects within well-defined nanoscale regions. The characterization of these atomic scale defects is challenging, and the mechanism for the emergence of ferromagnetism due to sensitive lattice disordering is unclear. Here we directly probe a variety of microscopic defects in systematically disordered B2 FeRh thin films that are initially antiferromagnetic and undergo a thermally-driven isostructural phase transition to a volatile ferromagnetic state. We show that the presence of static disorder i.e., the slight deviations of atoms from their equilibrium sites is sufficient to induce a non-volatile ferromagnetic state at room temperature. A static mean square relative displacement of 9.10-4 Å-2 is associated with the occurrence of non-volatile ferromagnetism and replicates a snapshot of the dynamic disorder observed in the thermally-driven ferromagnetic state. The equivalence of static and dynamic disorder with respect to the ferromagnetic behavior can provide insights into the emergence of ferromagnetic coupling as well as achieving tunable magnetic properties through defect manipulations in alloys.

Permalink: https://www.hzdr.de/publications/Publ-30773
Publ.-Id: 30773


Accurate MR image registration to anatomical reference space for diffuse glioma

Visser, M.; Petr, J.; Müller, D. M.; Eijgelaar, R. S.; Hendriks, E. J.; Witte, M.; Barkhof, F.; van Herk, M.; Mutsaerts, H. J.; de Munck, J. C.; Vrenken, H.; de Witt Hamer, P. C.

To summarize the distribution of glioma location within a patient population, registration of individual MR images to anatomical reference space is required. In this study, we quantified the accuracy of MR image registration to anatomical reference space with linear and non-linear transformations using estimated tumor targets of glioblastoma and
lower-grade glioma, and anatomical landmarks at pre- and post-operative time-points using six commonly-used registration packages (FSL, SPM5, DARTEL, ANTs, Elastix, and NiftyReg). Routine clinical pre- and post-operative, post-contrast T1-weighted images of 20 patients with glioblastoma and 20 with lower-grade glioma were collected. The 2009a
Montreal Neurological Institute brain template was used as anatomical reference space. Tumors were manually segmented in the patient space and corresponding healthy tissue was delineated as a target volume in the anatomical reference space. Accuracy of the tumor alignment was quantified using the Dice score and the Hausdorff distance. To measure the accuracy of general brain alignment, anatomical landmarks were placed in patient and in anatomical reference space, and the landmark distance after registration was quantified. Lower-grade gliomas were registered more accurately than glioblastoma. Registration accuracy for pre- and postoperative MR images did not differ. SPM5 and DARTEL registered tumors most accurate, and FSL least accurate. Non-linear transformations resulted in more accurate general brain alignment than linear transformations, but tumor alignment was similar between linear and non-linear transformation. We conclude that linear transformation suffices to summarize glioma locations in anatomical reference space.

Permalink: https://www.hzdr.de/publications/Publ-30772
Publ.-Id: 30772


On the O-rich domain of the U-Am-O phase diagram

Epifano, E.; Vauchy, R.; Lebreton, R.; Lauwerier, F.; Joly, A.; Scheinost, A.; Guéneau, C.; Valot, C.; Martin, P. M.

Uranium–Americium oxides U1−yAmyO2±x are promising candidates as possible transmutation targets for next generation nuclear reactors. In the context of a comprehensive investigation of their thermodynamic and thermal properties, the behaviour in oxidizing conditions is here studied. In a recent work, the behaviour in air of stoichiometric and sub-stoichiometric U1−yAmyO2−x compounds, with various Am content, was investigated by high-temperature X-ray Diffraction. Herein, the hyper-stoichiometric oxides obtained from that study are investigated by X-ray Absorption Spectroscopy. The new data, together with the previous XRD results, allow determining the exact compositions of the samples and hence obtaining phase diagram points in the O-rich domain of the U-Am-O system. Indeed, five phase diagram points at 1473 K are obtained: two tie-lines in the M4O9-M3O8 domain, for Am/(Am + U) = 0.10 and 0.15, one tie line in the MO2+x-M3O8 domain, for Am/(Am + U) = 0.28, and two points in the single phase MO2±x domain, for higher americium concentration. From these data, it is also concluded that trivalent americium has a small solubility in the M4O9 and M3O8 phases.

Keywords: transmutation; nuclear fuel; XANES; EXAFS

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-30771
Publ.-Id: 30771


Terahertz absorption-saturation and emission from electron-doped germanium quantum wells

Ciano, C.; Virgilio, M.; Bagolini, L.; Baldassarre, L.; Pashkin, O.; Helm, M.; Montanari, M.; Persichetti, L.; Di Gaspare, L.; Capellini, G.; Paul, D. J.; Scalari, G.; Faist, J.; de Seta, M.; Ortolani, M.

We study radiative relaxation at terahertz frequencies in n-type Ge/SiGe quantum wells, optically pumped with a terahertz free electron laser. Two wells coupled through a tunneling barrier are designed to operate as a three-level laser system with non-equilibrium population generated by optical pumping around the 1→3 intersubband transition at 10 THz. The non-equilibrium subband population dynamics are studied by absorption-saturation measurements and compared to a numerical model. In the emission spectroscopy experiment, we observed a photoluminescence peak at 4 THz, which can be attributed to the 3→2 intersubband transition with possible contribution from the 2→1 intersubband transition. These results represent a step towards silicon-based integrated terahertz emitters.

Permalink: https://www.hzdr.de/publications/Publ-30769
Publ.-Id: 30769


Strömungsmorphologie flashender Feeds bei kritischen Stoffwerten

Döß, A.; Schubert, M.; Wiezorek, M.; Hampel, U.; Flegiel, F.; Windmeier, C.; Schleicher, E.

Eine gängige Methode zur Konditionierung von Zulaufströmen in Rektifikations-kolonnen ist die Entspannungsverdampfung (flash) des Feedstroms mit nachgeschalteter oder integrierter Separation der kontinuierlichen und dispersen Phasenanteile. Die Gestaltung der Einspeisung in die Kolonne sowie die Auswahl von Einleitorganen erfordert eine möglichst exakte Vorhersage der sich einstellenden Strömungsmorphologie in der Feedleitung. Verfügbare Strömungsdaten beschränken sich fast ausschließlich auf Wasser-Luft-Systeme bei geringen Rohrdurchmessern (< DN100) und großen Einlauflängen (> 40 D). Deren Übertragbarkeit auf organische oder kryogene Systeme mit z. B. deutlich geringeren Grenzflächenspannungen für praxisnahe Rohrdimensionen unterliegt dabei großen Unsicherheiten. Zur Untersuchung flashender Feeds wurde daher ein Kältemittel-Versuchsstand im Technikums¬maßstab entwickelt. Das Arbeitsfluid wird durch eine Armatur in eine horizontale Feedleitung (DN200, Länge 20 D) entspannt und tritt als Zweiphasenströmung in die nachgeschaltete Kolonne ein. Die Dampfanteile nach der Entspannungsverdampfung werden über die jeweiligen Betriebsdrücke und -temperaturen mittels Elektroerhitzer und Kreislaufpumpe eingestellt, während der Betriebsdruck in der Teststrecke über einen Kondensator im Kopfstrom der Kolonne geregelt wird. Als Betriebsmedium wird das Kältemittel 3M™ Novec™649 eingesetzt, dessen Grenzflächenspannung in einem Bereich von 2 bis 8 mN m-1 bei einer Dichtedifferenz zwischen Dampf und Flüssigkeit von 800-1500 kg m-3 bei Betriebstemperaturen bis 140 °C eingestellt werden kann. Die Charakterisierung der sich entwickelnden Strömungsmorphologie in der horizontalen Feedleitung erfolgt mittels zeitlich und räumlich hochauflösender Gittersensormesstechnik. Schwerpunkte der Untersuchungen sind dabei die axiale Entwicklung der Strömungsform zwischen Entspannungsarmatur und Kolonneneintritt sowie die Bestimmung der Phasenanteile und Strömungs¬druck¬ver-luste
Diese Arbeit findet im Rahmen des Projektes TERESA statt und wird durch das Bundesministerium für Wirtschaft und Energie (BMWI) gefördert (FKZ 03ET1395D).

  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik, Adsorption und Extraktion 2020, 25.-28.02.2020, Berchtesgaden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30768
Publ.-Id: 30768


Formation of Thin NiGe Films by Magnetron Sputtering and Flash Lamp Annealing

Begeza, V.; Mehner, E.; Stöcker, H.; Xie, Y.; García, A.; Hübner, R.; Erb, D.; Zhou, S.; Rebohle, L.

The nickel-monogermanide (NiGe) phase is known for its electrical properties such as low ohmic and low contact resistance in group-IV-based electronics. In this work, thin films of nickel germanides (Ni-Ge) were formed by magnetron sputtering followed by flash lamp annealing (FLA). The formation of NiGe was investigated on three types of substrates: on amorphous (a-Ge) as well as polycrystalline Ge (poly-Ge) and on monocrystalline (100)-Ge (c-Ge) wafers. Substrate and NiGe structure characterization was performed by Raman, TEM, and XRD analyses. Hall Effect and four-point-probe measurements were used to characterize the films electrically. NiGe layers were successfully formed on different Ge substrates using 3-ms FLA. Electrical as well as XRD and TEM measurements are revealing the formation of Ni-rich hexagonal and cubic phases at lower temperatures accompanied by the formation of the low-resistivity orthorhombic NiGe phase. At higher annealing temperatures, Ni-rich phases are transforms into NiGe, as long as the supply of Ge is ensured. NiGe layer formation on a-Ge is accompanied by metal-induced crystallization and a decline of its electrical conductivity compared with that of poly-Ge and c-Ge substrates. Specific resistivities for 30 nm Ni on Ge were determined to be 13.5 uOhm cm for poly-Ge, 14.6 uOhm cm for c-Ge and 20.1 uOhm cm for a-Ge.

Keywords: germanium; germanides; nickel; thin films; sputtering; flash lamp annealing

Permalink: https://www.hzdr.de/publications/Publ-30767
Publ.-Id: 30767


Thermo-mechanical modelling of reactor pressure vessel during core melt invessel retention

Villanueva, W.; Filippov, A.; Jules, S.; Lim, K.; Jobst, M.; Bouydo, A. M.; Qais, S.; Wang, H.; Fichot, F.; Bechta, S.

Thermo-mechanical behavior of ablated reactor pressure vessel (RPV) during in-vessel melt retention is assessed. Specifically, we provide a preliminary synthesis of a benchmark exercise on a generic Pressurized Water Reactor (PWR) RPV with external water cooling. A two-layer pool configuration with a molten metal layer atop, reaching a local heat flux of 2 MW/m² on the vessel wall is assumed reflecting a focusing effect which in turn results in a thin ablated wall with remaining thickness of 16 mm. The aim is to investigate the effect of internal pressure on the structural integrity of the RPV. A total of 7 contributions from different organizations using 5 different codes are analyzed. The results are divided into low internal pressure cases where no vessel failure is expected, and high internal pressure cases where vessel failure is found based on specific failure criteria applied by the users. At 3 bar internal pressure, all the results reflecting stresses and strains indicate no vessel failure. Four contributions found vessel failures at internal pressure of 40, 45, 50, and 52 bars. The mode of failure in all calculations is the same, which is plastic instability caused by high stresses, although the failures are indicated by different criteria. Further, the results are compared against a simplified approach and reasonable agreement is found. Finally, a preliminary failure map is generated to demonstrate the applicability of a previously proposed methodology that utilizes a safety criterion based on the relation between the minimum vessel thickness and the maximum internal load.

  • Contribution to proceedings
    International Seminar “In-vessel retention: outcomes of IVMR project”, 21.-22.01.2020, Juan-les-Pins, France
    Proceedings of the International Seminar “In-vessel retention: outcomes of IVMR project”

Permalink: https://www.hzdr.de/publications/Publ-30766
Publ.-Id: 30766


Collision probability of fine particles in the bubble wake - An experimental study with 4D particle tracking velocimetry

Sommer, A.-E.; Heitkam, S.; Eckert, K.

One highly relevant challenge in flotation is the recovery of fine particles. Due to their low inertia, these particles are mostly pushed aside by rising bubbles. Consequently, they typically exhibit low probability for bubble-particle collision and thus, a poor recovery rate. In this work, the trajectories of fine particles in the vicinity of rising bubbles were investigated. The measurements considered a chain of millimetric bubbles within a rectangular container filled with deionized water. The flow field near the bubbles was measured by tomographic particle image velocimetry (TPIV), employing fluorescent tracer particles of 33µm diameter. Subsequently, trajectories of larger particles and bubble-particle collision events are recorded with 4D particle tracking velocimetry using a high temporal and spatial resolution. The results reproduce the well-known collision of particles on the leading edge of a rising bubble. Additionally, collisions on the tailing edge were observed in cases with a low Stokes number. The TPIV results demonstrate, that the high turbulent kinetic energy in the bubble wake allows particles to divert from the fluid streamlines and collide with the tailing edge of the bubble. The tailing edge collision probability increases with the Reynolds number and with decreased particle inertia. Overall, the investigation shows that the collision of fine particles in the bubble wake should be considered for the development of further collision probability models. Furthermore, the importance of turbulence on the fine particle flotation was demonstrated.

Keywords: 4D Particle tracking velocimetry (PTV); tomographic particle image velocimetry (TPIV); fine particle flotation; collision probability; Bubble-particle interaction; wake induced collision

  • Contribution to proceedings
    XXX International Mineral Processing Congress in Cape Town, 18.-22.10.2020, Kapstadt, Südafrika
    Proceedings of the XXX. International Mineral Processing Congress

Permalink: https://www.hzdr.de/publications/Publ-30765
Publ.-Id: 30765


In-depth 3D characterization of sieve tray hydrodynamics

Vishwakarma, V.; Abdul Haq, S.; Schubert, M.; Schleicher, E.; Hampel, U.

Understanding the tray hydrodynamics is important for their effective design as well as for the assessment of their separation performance. Currently, the clear liquid height is considered as one of the most important hydrodynamic parameters [1]. For example, it is utilized to correlate dispersion density, liquid entrainment rate, weeping flux and flow regime transitions. This height is usually measured at a point on the tray floor by continuously flushing out the liquid into the manometer. It is debatable whether such point reading is representative for the true liquid content on large trays or three-dimensional analyses should be performed. For this purpose, a sieve tray column (800 mm dia.) mockup facility is used in this work with air and tap water at respective loadings of 1.4 – 2.0 Pa0.5 and 1.0 – 3.0 m3/h that correspond to the froth regime.

A novel conductivity-based sensor [2] is developed for the 3D two-phase flow quantification at high spatial and temporal resolution. Basically, the local phase holdups at multiple locations along the sensor measurement plane and at different dispersion heights are determined here. It is assessed if the integration of the holdup profiles can lead to better estimates of the clear liquid height. Pressure drops and weeping rates are also measured. Furthermore, stimulus-response experiments with de-ionized water as tracer are performed at selective dispersion heights for identifying the flow profiles via residence time distribution.

These new 3D tray hydrodynamic data may also serve as a reference for establishing CFD models in the future, which so far have largely relied either on clear liquid height data only or on the low resolution data of Solari and Bell [3].

[1] Lockett, M.J., 1986. Distillation tray fundamentals.
[2] Vishwakarma, V., Schleicher, E., Schubert, M., Tschofen, M. and Löschau, M., Deutsche Patentanmeldung DE 10 2018 124 501.7, Sensor zur Vermessung von Strömungsprofilen in großen Kolonnen und Apparaten.
[3] Solari, R.B. and Bell, R.L., 1986. Fluid flow patterns and velocity distribution on commercial‐scale sieve trays. AIChE journal, 32(4), pp.640-649.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik, Adsorption und Extraktion, 26.-28.02.2020, Berchtesgaden, Germany

Permalink: https://www.hzdr.de/publications/Publ-30764
Publ.-Id: 30764


Application of Positron Emission Particle Tracking (PEPT) to measure the bubble-particle interaction in a turbulent and dense flow

Sommer, A.-E.; Ortmann, K.; van Heerden, M.; Richter, T.; Leadbeater, T.; Cole, K.; Heitkam, S.; Brito-Parada, P. R.; Eckert, K.

In a flotation cell, turbulence influences the motion of solid particles relative to the bubble surface, and, thus, affects the recovery rate. But, the impact of turbulence on the probability of a bubble-particle aggregation is still difficult to measure, especially in a dense flow. Therefore, the focus of this work was to apply PEPT as a method to investigate the effect of turbulence on the particle movement and bubble-particle interaction in an opaque flow. Single air bubbles (db=2.5 mm) were generated on a needle in a water flow channel. Upstream, a grid produced an isotropic turbulent flow with 5% to 15% turbulence intensity and a Kolmogorov microscale of 20µm. Depending on the distance to the grid, the flow near the captive bubble (Reb~450) was characterized by eddies of different length scales and magnitude with tomographic PIV. The solid suspension contained up to 0.3% PMMA particles (dp=200-400µm) and up to six radiolabelled particles (dp=300-400µm) coated with PMMA. The trajectories of the labelled particles were used to determine the average particle distribution in the turbulent field and describe the bubble-particle interactions. These results provide valuable information on the applicability of PEPT in turbulent and dense flow fields as well as on particle trajectories close to bubbles, enhancing our understanding of key flotation phenomena.

Keywords: Positron Emission Particle Tracking (PEPT); tomographic Particle Image Velocimetry (PIV); bubble-particle interaction; grid turbulence; dense flow; flotation

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  • Secondary publication expected from 01.09.2021

Permalink: https://www.hzdr.de/publications/Publ-30763
Publ.-Id: 30763


INSPIRE: A multi-centric study to harmonize linear energy transfer (LET) calculations for biological assessments of proton therapy plans

Ödén, J.; Hahn, C.; Vestergaard, A.; Jensen, M. F.; Sokol, O.; Pardi, C.; Bourhaleb, F.; Leite, A.; de Marzi, L.; Rose, C.; Merchant, M.; Grzanka, L.; Dasu, A.; Lühr, A.

Purpose: Emerging clinical evidence supports the variability of relative biological effectiveness (RBE) in proton radiotherapy. This poses the need to account for RBE variability in proton planning. However, no harmonized concept exists on how to calculate the RBE-driving linear energy transfer (LET) in clinical practice. Therefore, a multi-centric study was set up with the objective to standardize clinical LET calculations in Europe.

Methods: Eight European institutions generated non-robust SOBP plans using common strict dose objectives. Multiple treatment field arrangements (single-field SOBP, perpendicular fields, opposing fields) were employed to cover a target cube in a water phantom. Each institution used its preferred treatment planning software and provided dose and corresponding LET distributions for a joint analysis.
Subsequently, RBE-weighted dose (DRBE) distributions were calculated for the single-field SOBP of one institution assuming the Wedenberg RBE model using Monte Carlo calculated unrestricted dose- and track-averaged LET (LETd/LETt) distributions considering (1) only primary protons, (2) all protons, (3) all particles with Z≤2.

Results: Institutional SOBP ranges and target average doses agreed within 2%. In contrast, near-minimum, average and near-maximum LETd differed up to 30%, 19% and 5% in the target, respectively. These discrepancies could partially be explained by different algorithms (Monte Carlo/analytical) and by different ions included in the LETd calculations.
LETd calculations were more sensitive to the considered secondary particle spectrum than LETt. Deriving DRBE using LETd yielded 0-11%, 4-12% and 12-45% higher DRBE in the entrance, target and distal edge regions, respectively, compared to LETt. The biological range extension using LETd (and LETt) was approximately 3 mm (and 1 mm).

Conclusions: Despite comparable dose distributions, substantial LET differences occurred among the participating institutions. These differences hamper the consistent analyses of clinical follow-up data as they translate to substantial discrepancies in predicted DRBE. Therefore, standardization of clinical LET calculations is of utmost importance.

  • Poster (Online presentation)
    2020 Joint AAPM/COMP Meeting, 12.-16.07.2020, Vancouver, Canada

Permalink: https://www.hzdr.de/publications/Publ-30761
Publ.-Id: 30761


2D and 3D convolutional neural networks for outcome modelling of locally advanced head and neck squamous cell carcinoma

Starke, S.; Leger, S.; Zwanenburg, A.; Leger, K.; Lohaus, F.; Linge, A.; Schreiber, A.; Kalinauskaite, G.; Tinhofer, I.; Guberina, N.; Guberina, M.; Balermpas, P.; von der Grün, J.; Ganswindt, U.; Belka, C.; Peeken, J. C.; Combs, S. E.; Böke, S.; Zips, D.; Richter, C.; Troost, E. G. C.; Krause, M.; Baumann, M.; Löck, S.

These are the results from the analyses presented in a paper submitted to Scientific Reports.

The zip file contains the trained model files and the plots that were used in the manuscript.

Code for reproduction of our analyses can be obtained from https://github.com/oncoray/cnn-hnscc. There, you also find instructions on how to load our models.

Keywords: convolutional neural networks; Keras; Deep learning; head and neck cancer; loco-regional-recurrence; Cox proportional hazards

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-02-27
    DOI: 10.14278/rodare.254
    License: CC-BY-NC-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30759
Publ.-Id: 30759


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